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Post by southernskies on Apr 28, 2020 2:14:22 GMT
Hi All
Feeling bored during these long days of home confinement due to Covid19? Maybe this can help you while away some time - or at least send you off to sleep.
Keep well
David
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Post by davy on Apr 28, 2020 6:32:07 GMT
Not boring at all, I enjoyed it,, I like seeing presentations like this posted, well done
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Post by Dragon Man on Apr 28, 2020 14:52:17 GMT
Excellent video David! I am amazed, you are using the same gear as me (except the mount, I use an EQ6). I also use a 6 inch f/5 Newtonian Astrograph, an IMX178 colour uncooled camera, the Toupsky/RisingSky software, Synscan WiFi adaptor, and even an HP Pavilion laptop
But what amazes me is that you manage to use a Focal Reducer yet get no Coma. Unless you are hiding a Paraccor or Coma Corrector in there somewhere
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iannz
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Post by iannz on Apr 28, 2020 21:22:09 GMT
hi David, great to watch! Not too sleep-inducing, maybe some background sounds from that soothing ozzie group, ACDC? Seriously, it was nice to see a sequence of actions and results from various tweaks. Gave me plenty more to think on and explore. Thanks for the video cheers ian
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Post by Deleted on Apr 29, 2020 2:10:21 GMT
Great video David.Also good to put a name to southernskies who keeps posting these fantastic images.
Like Ken, I am very interested as to what focal reducer you are using. At f3.4 that makes it about .7fr.
I have a 6"gso f4 newt otherwise have the same gear as you ,but my images do not compare. The newts certainly give much crisper images than what I can get with my sct's but my f4 newt needed constant collimation. That is the main reason it is sitting in the shed with cobwebs .I need to give it another go. cheers Paul
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Post by southernskies on Apr 29, 2020 3:51:59 GMT
Thanks for you comments Davy, Ken, Ian and Paul.
As to the focal reducer, I’ve tried a number of units in the past but for the f/5 Newt the best solution I’ve found is to use the front part of the two-part Mallincam MFR5. The front part at x0.68 is more powerful than the back part at about x0.80. In combination they give something like x0.50 and even less if you use the supplied spacer rings. But I found that using both parts together produced unwanted coma. Using either the back part or the front part by itself works just fine but I prefer the front part for two reasons. The first and most obvious reason is that it gives the greater focal reduction. The second reason is that the barrel of the front part is longer than the barrel of the back part. So it easily replaces the conventional nosepiece that came with the camera. Looking at Mallincam’s website it seems that one can now buy the front part as a separate unit. It goes by the designation MFR3. At US$250 the MFR5 is a pricey unit. Even the MFR3 is US$140. But whichever one is chosen, once bought it should last a lifetime.
Edit : On reflection, the problem with using both parts of the MFR5 was not so much coma as the fact they inevitably increase the distance between the top of the focuser and the camera’s sensor than is the case if just one part is used. With both parts in play the focuser needs to be racked in to just about its limit and that has the result that the focuser barrel intrudes inward into the optical tube to the extent that it blocks a significant amount of light from reaching the primary mirror and also quite seriously degrades the quality of the image.
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Post by Dragon Man on Apr 29, 2020 9:52:33 GMT
THanks for the info David. I will try the front element of my MFR-5. I tested using several 0.5x FR's and they all gave bad Coma, so that is why I ended up not using an FR at all. I didn't think to try the MFR-5 elements separately. Thanks for the tip
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Post by Deleted on Apr 29, 2020 22:21:40 GMT
Same here.I havent used the MFR-5 since I got rid of my Mallincams. Thanks for the tip. Now I have to get some consistency with the collimation of the newt. I get different results using the cheshire to the laser . cheers Paul
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Post by howie1 on Apr 30, 2020 1:01:17 GMT
Same here.I havent used the MFR-5 since I got rid of my Mallincams. Thanks for the tip. Now I have to get some consistency with the collimation of the newt. I get different results using the cheshire to the laser . cheers Paul Bingo ... you've found out why lasers are IMO crap. The lasers themselves are usually manufactured and delivered out of collimation!!!! The laser beam should always point to the same spot if you rotate it 360 degrees. They dont. Over 5000mm mine made a 25mm diameter circle. Which meant in my 1000mm focal length Newt the primary mirror adjustment is based on the laser travelling 1000mm to the mirror then another 1000mm back to the lasers bullseye target. Over that 2m the laser was therefore a full cm off target! I should have actually placed the reflected dot on the bullseye a full 1cm in some direction away from the bullseye, to actually be collimated! But in which direction? Cheshire and the standard collimation cap on the other hand, rely on light .... which always travels in straight lines ... and the fact that only if a mirror is absolutely perpendicular to the light, will the reflected light travel back upon itself on the exact same path. Paul, definitely (!!!!) use the cap with hole, or a cheshire which uses the same principle. Sell the laser. I struggled for quite a while with the secondary mirror ... you can move in in and out of the tube, adjust the three grub screws to change its angle in any direction, and also turn it to and fro across the aperture. Three separate degrees of freedom! And change any one and the other two have to be readjusted. That's the one which freaked me out .... until I discovered Astrobaby's web article on collimating a newtonian telescope where she says to place colored cardboard behind the secondary and bingo it all became much easier. Google for it . The color makes the secondary stand out and so much easier to orientate correctly. A bit of practise and it becomes literally as easy as 1 2 3 ... you're done. Leastwise it was a revelation for shortening my learning and frustration curve! Cheers, Howie
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Post by howie1 on Apr 30, 2020 1:22:13 GMT
You guys and your coma issues! We're doing EAA with little detail compared to AP, and heaps of noise compared to AP, and cheap equipment compared to AP ... to observe rather than get AP shots ... who cares about a little coma! Ages back when I still used Mallincam, I tested every combination of element and spacer I had on hand for the MFR5. Photo below shows the little table which I laminated and keep in the bag with the MFR5. May be of use to some of you. Coincidence and I was actually out last night with Star Adventurer, ST80, ASI224 plus the MFR5 operating at f1.5 .... The ST80 native 400mm at f5 + MFR5 set to 0.3x reduction on top of that for 120mm FL at f1.5 ... Great fun. Didnt save any shots or anything just out mucking around. Grainy noisy shots and wind blowing the ST80 around as that is heavy for the little star adventurer to hold still at the best of times let alone wind. But heaps of fun.
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Post by davy on Apr 30, 2020 3:44:19 GMT
Same here.I havent used the MFR-5 since I got rid of my Mallincams. Thanks for the tip. Now I have to get some consistency with the collimation of the newt. I get different results using the cheshire to the laser . cheers Paul Bingo ... you've found out why lasers are IMO crap. The lasers themselves are usually manufactured and delivered out of collimation!!!! The laser beam should always point to the same spot if you rotate it 360 degrees. They dont. Over 5000mm mine made a 25mm diameter circle. Which meant in my 1000mm focal length Newt the primary mirror adjustment is based on the laser travelling 1000mm to the mirror then another 1000mm back to the lasers bullseye target. Over that 2m the laser was therefore a full cm off target! I should have actually placed the reflected dot on the bullseye a full 1cm in some direction away from the bullseye, to actually be collimated! But in which direction? Cheshire and the standard collimation cap on the other hand, rely on light .... which always travels in straight lines ... and the fact that only if a mirror is absolutely perpendicular to the light, will the reflected light travel back upon itself on the exact same path. Paul, definitely (!!!!) use the cap with hole, or a cheshire which uses the same principle. Sell the laser. I struggled for quite a while with the secondary mirror ... you can move in in and out of the tube, adjust the three grub screws to change its angle in any direction, and also turn it to and fro across the aperture. Three separate degrees of freedom! And change any one and the other two have to be readjusted. That's the one which freaked me out .... until I discovered Astrobaby's web article on collimating a newtonian telescope where she says to place colored cardboard behind the secondary and bingo it all became much easier. Google for it . The color makes the secondary stand out and so much easier to orientate correctly. A bit of practise and it becomes literally as easy as 1 2 3 ... you're done. Leastwise it was a revelation for shortening my learning and frustration curve! Cheers, Howie www.cloudynights.com/topic/463465-diy-collimation-webcam-you-need-this/
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Post by Dragon Man on Apr 30, 2020 6:51:15 GMT
You guys and your coma issues! We're doing EAA with little detail compared to AP, and heaps of noise compared to AP, and cheap equipment compared to AP ... to observe rather than get AP shots ... who cares about a little coma! Ages back when I still used Mallincam, I tested every combination of element and spacer I had on hand for the MFR5. Photo below shows the little table which I laminated and keep in the bag with the MFR5. May be of use to some of you. Coincidence and I was actually out last night with Star Adventurer, ST80, ASI224 plus the MFR5 operating at f1.5 .... The ST80 native 400mm at f5 + MFR5 set to 0.3x reduction on top of that for 120mm FL at f1.5 ... Great fun. Didnt save any shots or anything just out mucking around. Grainy noisy shots and wind blowing the ST80 around as that is heavy for the little star adventurer to hold still at the best of times let alone wind. But heaps of fun. Howie, with the focal reducers I tested (all el-cheapo crap) I was getting a bit more than a little Coma problem. My Coma went all the way to the centre of the image I was having trouble finding a round star anywhere in the frame and the outer stars were complete disasters I really don't care too much about the quality of a Live frame as often it helps prove the view is live, but when the image looks more like doing Warp 5 on Star Trek, then I reject it That's why I don't have any saved images to show how bad it is in my setup. Thanks for the table. I have a wonderful high grade 2.7 inch 0.7x Telecompressor (Focal Reducer) but it only fits my 6 inch f/5 refractor 2.7 inch focuser It works great in the refractor, but I can't use it in the Reflector.
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Post by howie1 on Apr 30, 2020 21:35:43 GMT
Yeah Ken, I'd probably complain too if all the stars were crap in the FOV!
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Post by Deleted on May 2, 2020 8:43:12 GMT
Bingo ... you've found out why lasers are IMO crap. The lasers themselves are usually manufactured and delivered out of collimation!!!! The laser beam should always point to the same spot if you rotate it 360 degrees. They dont. Over 5000mm mine made a 25mm diameter circle. Which meant in my 1000mm focal length Newt the primary mirror adjustment is based on the laser travelling 1000mm to the mirror then another 1000mm back to the lasers bullseye target. Over that 2m the laser was therefore a full cm off target! I should have actually placed the reflected dot on the bullseye a full 1cm in some direction away from the bullseye, to actually be collimated! But in which direction? Cheshire and the standard collimation cap on the other hand, rely on light .... which always travels in straight lines ... and the fact that only if a mirror is absolutely perpendicular to the light, will the reflected light travel back upon itself on the exact same path. Paul, definitely (!!!!) use the cap with hole, or a cheshire which uses the same principle. Sell the laser. I struggled for quite a while with the secondary mirror ... you can move in in and out of the tube, adjust the three grub screws to change its angle in any direction, and also turn it to and fro across the aperture. Three separate degrees of freedom! And change any one and the other two have to be readjusted. That's the one which freaked me out .... until I discovered Astrobaby's web article on collimating a newtonian telescope where she says to place colored cardboard behind the secondary and bingo it all became much easier. Google for it . The color makes the secondary stand out and so much easier to orientate correctly. A bit of practise and it becomes literally as easy as 1 2 3 ... you're done. Leastwise it was a revelation for shortening my learning and frustration curve! Cheers, Howie Gidday Howie, the caps with a hole are not easy to come by. I made one myself and it was useless crap. I agree with the secondary mirror problems. I was getting into all sorts of trouble. I read Astrobaby's article in the past . Although it made sense, It is very fiddly with a 6 inch newt. It is hard to get the paper in and out past the spider vanes. It is much easier with the 8" but the it is a bit too heavy for the HEQ5. After seeing David's images I am keen to give the newt another go. The sct's just dont give you the pinpoint stars of a newt. cheers Paul
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Post by Deleted on May 3, 2020 5:48:11 GMT
I cleaned the cobwebs off the 8" and the 6" newts and then collimated both. Both were pretty good from last time I used them a couple of years back.. I guess I followed the Starizona instructions on collimation most of all but read the advice of a number of others including Astrobaby. Thanks Howie. The 8" will probably gather cobwebs again but the 6" sits nicely on the heq5 I used a collimation cap( forgotten I had bought one) for the focuser/secondary rotation issues,followed by the laser collimator for secondary tilt and primary alignment and then finally the cheshire to fine tune the primary. It sounds like a lot of work but when the collimation was pretty good to start with it actually only took a few minutes. So, no excuses ,I now need to produce the goods. If I can get the images looking something like yours, David,I will be pretty happy. A bit of decent weather would help cheers Paul
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Post by Deleted on May 4, 2020 0:46:44 GMT
Well , last night was a disaster. The moon was bright, coma on the newt extended right into the centre of the field, the HEQ5 goto was awful, and then the clouds rolled in. But,learnt a few things. The A part of the MFR plus an F4 newt is not a good combination. Coma was terrible. This disappeared when I removed it but then the clouds rolled in. I have to be more careful with balancing the newt on the heq5. The goto accuracy was severely affected. This was after pretty accurate polar alignment with sharpcap. The balance of the sct's and the refractors is much more even than newts on the HEQ5. I would not even attempt to try the 8 " f4 on that mount. Fairly sure the collimation was ok once the focal reducer was removed.
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iannz
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Posts: 71
home town/country: Tarurutangi, NZ
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Post by iannz on May 4, 2020 1:38:14 GMT
Hey, at least you can tell your clouds apart from each other by the sounds of it. Been Stormy/wet here since yesterday and clouded for the last week or so getting to it..... life on an island. Interesting to hear about the newt balance comment. I have a GSO 10" dob that I intend to try on a mount I recently got so nice to know thanks. Have to check out the polar align re SC, wasn't aware it was an option, (hadn't gone looking). So many fronts to be working on it's a bit distracting/confusing but all part of the journey of course. A bad time of year to start I'm thinking, bit of a wait between suitable nights to observe. cheers ian
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Post by Deleted on May 4, 2020 23:38:06 GMT
Ian,I would not be able to polar align without Sharpcap or the ASiair. I was alt/az until then. Now I never use alt/az. Have an EQ6-R in the pod with the Rasa . It doesnt get moved so rarely have to polar align . That mount is great. It has a very accurate goto. My heq5 gets moved out of a shed every time so I have to polar align every time but it only takes 5 minutes with sharpcap. I find the goto of the heq5 is very accurate with a small scope but struggles with accuracy over about 6kg. Yesterday I spent a long time fiddling with collimators on the newt. You will be pleased to know Howie I put the white paper over the primary and the red paper opposite the focuser and rotated and tilted the secondary to see what happened. I totally wrecked what was good collimation but I think I fixed it ok.This time the difference between the laser and the paper/collimation cap combination on the secondary was more marked than the day before . So I went with the circular secondary and collimation cap. Then used the collimation cap and the cheshire on the primary and totally ignored the laser. Last night was clear but the moon was very bright. I tried the zwo 178 with the .7fr again on the newt. No go ..terrible coma, but at least the goto was better,but still not as good as with the other scopes. It is hard to get good balance of the newt on the heq5. So I was not sure how good the collimation was in the end. I was probably trying to do too many things in one night. I put the C6 with hyperstar on the heq5 with the zwo 290 mono plus the 642 to IR pass filter and pointed it at M65,hoping to block out a lot of moonlight. The moon was close by and could barely make out M65. So ,I have had 2 very unsuccessful viewing nights in a row,but I have learnt a few things. Mainly what not to do. Dont trust a laser collimator. The 2 lots of paper does help with secondary collimation. Focal reduction doesnt work on an F4 newt Be very careful with the balancing of a newt on a heq5 The 642to IR pass filter doesnt block out moonlight. and I got no decent images cheers Paul
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Post by howie1 on May 6, 2020 1:42:07 GMT
Ian,I would not be able to polar align without Sharpcap or the ASiair. Be very careful with the balancing of a newt on a heq5 Gday Paul. While I always found that the PA routine built into the hand control worked a treat, once the PA routine appeared in sharpcap I havent used the HC routine again! My old heq5 pro (now 13 years old BTW) had terrible backlash on RA. Fixed by .... 1. Rowan Astronomy belt drive kit for the HEQ5. If you get the kit be sure to get a spare set of belts too. They do stretch over time reintroducing backlash. But when new and unstretched they pretty much eliminate backlash. Also make the mount nice and quiet. Very simple to install. And more importantly than the Rowan belt .... 2. Balancing the newt properly. How many degree's away from your dovetail is the focuser? Is it 180 degrees away - IE directly opposite the dovetail? Or at an angle like +160 degrees? Or is the focuser at 90 degrees to the dovetail? For camera work the focuser should be 180 degree's from the dovetail bar. The focuser + camera + cables weighs much more than the finder, and so if you put camera + cables into the focuser in most normal positions (like 90 degrees from dovetail or 120 or 160 degrees) you will find the RA balance point is changing at every point over its motion from East to West. Whereas if you stick that big mass of focuser + camera + cables 180 degrees to the dovetail, it will suffer under/over balance conditions much less severely over its East to est RA rotation. Tough to think about ... but camera etc 180 degrees from the dovetail also means the DEC balance is also much more consistent too. As when DEC slews to different targets the weight is heavily moved around if the camera was at 90 degrees to the dovetail compared to if held 180 degrees to it. Lastly, the cable should come out of the camera and then be bent back along the OTA optical axis line to then turn right angles downwards right at the mounts DEC head centreline. IE cables route right down from bolts where you connect the dovetail to the DEC head and straight down through the EP tray holes to the ground below. Don't leave them hanging from the ends of the OTA where you inserted the camera. TIP .... I do not use the finder at all. With the focuser + camera 180 degrees from the dovetail and no finder on the OTA it means it is very nicely balanced right through the E-W RA motion. I put the finderguider + ZWO on to do the PA, then take if off leaving the main camera and OTA nicely balanced. I then do the star alignments using just the main camera and OTA. If the first star in that alignment is nowhere to be seen in the main camera then I fit a normal right angle eyeball finderscope to centre it, then remove that finder, as the first wayward star will then absolutely be in the FOV of the main scope. The second and third stars are always in the main camera FOV as that first star has corrected most of the alignment issues. Cheers, Howie
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Post by Deleted on May 6, 2020 10:59:39 GMT
Great advice Howie. That has never been explained to me before.The focuser is about 160 degrees and I have red dot finder attached at about 180 which is pretty light and right angle visual finder about another 20 degrees further. I thought this was about as balanced as possible but obviously not good enough. The newt is about 6kg and so is the lx90 8", but the 8" has always tracked better than the newt mainly because it was better balanced I guess.I will change the focuser to 180 degrees and attach the right angle finder only when I need it.
I had a look at installing the Rowan Astronomy Belt on youtube. I would be very worried about stuffing the mount up completely so I might hold off on that upgrade.
The newts are great value for money and produce good results but the fast ones need a lot of care and attention cheers Paul
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