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Post by Rick in NWArk on Mar 27, 2014 3:58:07 GMT
So... why VA? For me, my passion is driven by sharing the wonders of the universe with people who may not normally be exposed to it. I love watching broadcasts on NSN, but -no offense- it would be even more exciting for me to have the chat room full of non-astronomers. I see VA as a way for me to deliver this passion much more effectively than the traditional queue of people waiting to look at a colorless fuzzy in an eyepiece.
I am starting from scratch because I don't have an appropriate platform -- 8" dob & 80mm Acro on non-electronic mounts and a 102mm acro on a motorized but insufficient mount.
And while researching appropriate video platforms, I realized that I can start learning some basic astrophotography as well.
And for both, I'm interested in planetary and deep sky. Objects small and large. So that means either multiple scopes or a compromised single scope with a heck of a lot of focal reduction/amplification. Certainly if I end up with multiple scopes, they need to be piggybacked, as an additional mount is just out of the question for many reasons.
With both VA & VP, the biggest decision seems to be the mount. Stable and sturdy with an appropriate payload capacity, right? Well, I have seen recommendations that say your payload should be anywhere from <50% to <75% of the capacity of the mount. To me that's a killer, because I see a big price jump from a 40lb capacity mount to a 50lb capacity mount. And its really easy to surpass the 25lb mark when you have a scope + cam + guide scope + etc.
For longer focal lengths - planetary and very small dso's... 8" Carbon Fiber RCs are about 17lbs (1600mm f/l) 8" Metal RCs are about 25lbs (1600mm f/l) 8" Meade SCT is about 20lbs (2000mm f/l) 9.25" Celestron is about 20lbs (2350mm f/l)
And a shorter focal length options for medium and bigger objects... 65mm ED Quad 5lbs (420mm f/l) 80mm ED Carbon Fiber triplet 6lbs (480mm f/l)
So yeah its tough to balance weight for the mount, range of focal lengths for different object sizes.
And then I have the crazy thought of a small acho with an autoguider!! I'm not sure if I've even seen a piggybacked piggyback!
So say you have a 2x barlow and a .75 focal reducer. A combo of 8" CF RC and an 80ED triplet (23 lbs) would give us focal lengths of 360, 480, 960, 1200, 1600, and 3200. That's not too bad. 360mm gives you the full M42 on a Mallincam Jr Pro's CCD, and 3200mm gives an ok sized Jupiter, tho I'd like at least double that, for a real nice view.
And my pockets aren't bottomless -- I'd like to stay below $2500US.
I've backed away a little from AltAz SCTs due to AP limitations, even tho they are strong for visual. But an SCT OTA on a GEM isn't out of the picture.
Thanks in advance for letting me ramble a bit.
I'm not even sure what I haven't considered yet... I guess I keep hoping there is something that will help me narrow the decision down.
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Post by Dragon Man on Mar 27, 2014 5:16:17 GMT
G'day Grue, US$2500 will buy some serious VA kit! Even here in Australia where prices are waaayyyy above U.S. prices I can still buy some great VA and AP gear for $2500. One of them in that budget would be a Skywatcher (or Orion) EQ6 GoTo mount. But you can keep the cost even lower by getting a Skywatcher (Orion) HEQ5 Pro Synscan Goto Mount. The HEQ5 will still carry 35 lbs (16kg). I know quite a few people using the HEQ5 Pro for serious Astrophotography and can't fault it. Many reviews actually say the HEQ5 has more accurate GoTo's than it's big brother the EQ6 (which is what I have). However, no matter what mount you get, try avoid scopes with long tubes as 'Flexure' will make any mount seem bad. Flaxure is when the length of a scope uses leverage. Picture this: You have 2 lengths of 1 inch thick wooden dowel. One is 2 feet long, one is about 5 feet long (a broomstick). Now hold both at the very end. Wave them around. Which one is easy for you hand to move the dowel. The 2 foot long one obviously. Feel the strain on your wrist trying to wave around the longer one. That is the strain a long scope can do to the gears in a mount. Even the slightest breeze will make the long scope act like a sail, move it around, and stress the gears. To stay in budget, an ED80 Refractor is an excellent all-round scope for VA and AP. Yes, ED80's are very good for AP. They are still very popular. I use an ED80 for all my VA work. After the ED80 I would recommend an 8" RC (Mallincam's VRC8 comes to mind), but the RC will probably go over your budget after the mount. Depends on U.S. prices. I can only go on Aussie prices. Also, if you want to use Autoguiding if you also do AP, then you only need to attach a cheap 70mm Achro as a guidescope. They are cheap. Guidescopes don't have to be good scopes. All they need to do is see some stars. Even slightly out of focus. Examples of prices: The scope: www.telescopes.com/telescopes/optical-tubes/skywatcherpro80edaporefractorota1.cfmThe mount: sportstelescope.com/product.php?id_product=245Often sold as a package deal: www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-pro-heq5-pro.html
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Post by Rick in NWArk on Mar 27, 2014 13:42:40 GMT
Ken,
Thanks for all the suggestions!
Here is the crux of my concern: if I were to go with the VRC8 + 80EDT + 70 achro, I'm looking at 25+6+3 = 34lbs. Add a cam and guider and the rings etc. etc. and you are over 35 lbs. Now I'm over the EQ5 and probably over what the Orion Atlas EQ/G (40 lbs) can handle well. Maybe I can save 3-5 lbs with a carbon fiber RC, but still, is 30lbs payload on a 40lbs capacity mount too much for VA/AP??
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Post by Deleted on Mar 27, 2014 15:47:24 GMT
Great thread! Some very helpful info here for a new comer looking for advice. Just my 2 cents but remember and factor in the counter weights! They need to be added to the overall capacity from what I understand. I tried several times to find out the max weight capacity for my LX90. It seems there is no exact figure. Apparently with fork mounts the weight isn't anywhere near as important as having it correctly balanced. (Something I don't do lol) I'm loading it up with prob around 15kg including scope, cables camera dovetail rings counter weights etc. other than being seriously heavy to lift it seems to perform just as good as when it had nothing on it In alt/az I don't see star trials till I go over 55 sec exposures.
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Post by Dragon Man on Mar 27, 2014 16:20:01 GMT
Ken, Thanks for all the suggestions! Here is the crux of my concern: if I were to go with the VRC8 + 80EDT + 70 achro, I'm looking at 25+6+3 = 34lbs. Add a cam and guider and the rings etc. etc. and you are over 35 lbs. Now I'm over the EQ5 and probably over what the Orion Atlas EQ/G (40 lbs) can handle well. Maybe I can save 3-5 lbs with a carbon fiber RC, but still, is 30lbs payload on a 40lbs capacity mount too much for VA/AP?? Why would you want 3 scopes loaded up on a mount? You only need one for VA, and 2 for AP, the second one being a very light small cheap Guidescope. I wasn't aware you wanted to balance 3 scopes at the same time Also, avoid an EQ5 mount. The lowest you want to go is HEQ5. Big difference between the two.
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Post by Deleted on Mar 27, 2014 16:56:02 GMT
Another option for the guider is something like the orion magnificent mini guider. It is super small and lightweight and works well. I used to own one. I now guide with a modified 5x80 finder scope.
Personally I went for the 6" RC to save weight and the slightly larger FOV. But I do not do any planetary on this setup.
If you are determined to piggyback, I would go with Kens suggestion of an EQ6 GEM. For AP 30 pounds on a 40 pound capacity mount is a bit much. my setup weighs about 20 pounds and my mount is only capable for 30, but I just use for video. I have not had any issues at all.
Also with an 80ED refactor you will most likely not need any guiding for video or short exposure AP. Why not just use the ED80 to guide the 8"RC? and when you want wide views just don't guide.
Good luck! I had a similar goal, but decided instead to just focus on DSO. I like never having to swap out reducers/barlows and cameras. But I have a Dob I use for planetary.
regaeds,
hemmi
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Post by Rick in NWArk on Mar 27, 2014 17:11:42 GMT
Great thread! Some very helpful info here for a new comer looking for advice. Just my 2 cents but remember and factor in the counter weights! They need to be added to the overall capacity from what I understand. I tried several times to find out the max weight capacity for my LX90. It seems there is no exact figure. Apparently with fork mounts the weight isn't anywhere near as important as having it correctly balanced. (Something I don't do lol) I'm loading it up with prob around 15kg including scope, cables camera dovetail rings counter weights etc. other than being seriously heavy to lift it seems to perform just as good as when it had nothing on it In alt/az I don't see star trials till I go over 55 sec exposures. I don't think counterweights are included in the capacity specifications.
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Post by Rick in NWArk on Mar 27, 2014 17:15:35 GMT
Ken, Thanks for all the suggestions! Here is the crux of my concern: if I were to go with the VRC8 + 80EDT + 70 achro, I'm looking at 25+6+3 = 34lbs. Add a cam and guider and the rings etc. etc. and you are over 35 lbs. Now I'm over the EQ5 and probably over what the Orion Atlas EQ/G (40 lbs) can handle well. Maybe I can save 3-5 lbs with a carbon fiber RC, but still, is 30lbs payload on a 40lbs capacity mount too much for VA/AP?? Why would you want 3 scopes loaded up on a mount? You only need one for VA, and 2 for AP, the second one being a very light small cheap Guidescope. I wasn't aware you wanted to balance 3 scopes at the same time Also, avoid an EQ5 mount. The lowest you want to go is HEQ5. Big difference between the two. #1 - longer focal length VA/AP, #2 - shorter focal length VA/AP, #3 guidescope only -- on one mount.
versus
#1 - longer focal length VA/AP & #3 guidescope on one mount and #2 - shorter focal length VA/AP & #3 guidescope on second mount (or if you don't want to flip guidescopes back and forth, a #4 guidescope)
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Post by Rick in NWArk on Mar 27, 2014 17:21:30 GMT
Another option for the guider is something like the orion magnificent mini guider. It is super small and lightweight and works well. I used to own one. I now guide with a modified 5x80 finder scope. Personally I went for the 6" RC to save weight and the slightly larger FOV. But I do not do any planetary on this setup. If you are determined to piggyback, I would go with Kens suggestion of an EQ6 GEM. For AP 30 pounds on a 40 pound capacity mount is a bit much. my setup weighs about 20 pounds and my mount is only capable for 30, but I just use for video. I have not had any issues at all. Also with an 80ED refactor you will most likely not need any guiding for video or short exposure AP. Why not just use the ED80 to guide the 8"RC? and when you want wide views just don't guide. Good luck! I had a similar goal, but decided instead to just focus on DSO. I like never having to swap out reducers/barlows and cameras. But I have a Dob I use for planetary. regaeds, hemmi Thanks for these suggestions, Hemmi, I've thought about going with a finder solution, but I've heard that its not as good as having a real finder scope. I hadn't considered unguided when using the 80, I'll have to look into what people have produced that way.
I'd hate to drop down to a 6RC, because I just know that I'll immediately wish I had the 8.
Perhaps I'm over-ambitious and over-thinking this.
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Post by Deleted on Mar 27, 2014 18:16:24 GMT
I don't think counterweights are included in the capacity specifications. Hmmm are you sure about that one? i would have thought adding loads of weight with extra scopes, cams, cables etc that a heavier counter weight would need to be used? Putting yet more weight on the mount nah? Ive only ever had scopes that dont use counter weights so its all new to me. But i would find it odd that a weight capacity limit would exclude the heaviest thing on the mount?
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Post by Deleted on Mar 27, 2014 18:24:04 GMT
I don't think counterweights are included in the capacity specifications. Hmmm are you sure about that one? i would have thought adding loads of weight with extra scopes, cams, cables etc that a heavier counter weight would need to be used? Putting yet more weight on the mount nah? Ive only ever had scopes that dont use counter weights so its all new to me. But i would find it odd that a weight capacity limit would exclude the heaviest thing on the mount? From my understanding, when you get the weight capacity of the mount it does include the weights supplied with the scope. So basically the capacity for the mount is what you are allowed to add to the mount and counter weights supplied. The problem is, if you have lots of kit you may need more counter weights to balance it and it is the weight of these that needs to be considered, I think....
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Post by Rick in NWArk on Mar 27, 2014 19:33:02 GMT
Hmmm are you sure about that one? i would have thought adding loads of weight with extra scopes, cams, cables etc that a heavier counter weight would need to be used? Putting yet more weight on the mount nah? Ive only ever had scopes that dont use counter weights so its all new to me. But i would find it odd that a weight capacity limit would exclude the heaviest thing on the mount? From my understanding, when you get the weight capacity of the mount it does include the weights supplied with the scope. So basically the capacity for the mount is what you are allowed to add to the mount and counter weights supplied. The problem is, if you have lots of kit you may need more counter weights to balance it and it is the weight of these that needs to be considered, I think.... That's my understanding too, Spaced.
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Post by Deleted on Mar 27, 2014 19:54:09 GMT
The payload capacity is the weight carried by the dovetail/saddle. Counter balance weights are not part of this calculation at all.
cheers
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Post by Deleted on Mar 27, 2014 20:02:19 GMT
The payload capacity is the weight carried by the dovetail/saddle. Counter balance weights are not part of this calculation at all. cheers Crikey, I did not realise that! My mount has a payload of 18kg for imaging and 25kg for visual. Does this mean I could effectively have 50KG for visual as in Alt Az I have two dovetail saddles?
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Post by Rick in NWArk on Mar 27, 2014 20:49:36 GMT
My understanding is the reason you want <75% (or <50% by some) mount capacity is for longer period AP exposures where if the weight is closer to max, you can get more gear slippage / errors.
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Post by Deleted on Mar 27, 2014 21:11:22 GMT
Some great info here thanks for clarifying!
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Post by Deleted on Mar 27, 2014 21:30:27 GMT
I think the capacity specified for mounts errs on the side of caution. There is some truth that for long exposures its best to keep the weight down rather that max it out, but most mounts will handle a properly balanced system even when at the max. If your rig is balanced properly then it should move in RA and Dec with the lightest touch. Counterweights only balance out the scope and shouldn't add any extra pressure on bearings and gears unless you go really silly. I do think however that how the counterbalnce weights are used will have a bearing on whether they are included in the payload. For instance, a counterweight added to the counterweight shaft should have no negative effect on the payload on the dovetail, whereas the counter balance weights added to a C11 to balance the scope on an Alt Az mount will have to be added to the total capacity as they are attached to the actual scope.
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Post by Deleted on Mar 27, 2014 21:36:18 GMT
The payload capacity is the weight carried by the dovetail/saddle. Counter balance weights are not part of this calculation at all. cheers Crikey, I did not realise that! My mount has a payload of 18kg for imaging and 25kg for visual. Does this mean I could effectively have 50KG for visual as in Alt Az I have two dovetail saddles? No Idea how this works in Alt AZ. But In GEM mounts the payload is OTA side weight only!
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Post by Dragon Man on Mar 28, 2014 13:49:24 GMT
It depends on the Manufacturer whether they include or exclude the counterweights in the 'Payload' specs. Celestron doesn't include counterweights. Celestron list their capacity is US Pounds as "instrument weight". www.celestron.com/c3/support3/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=2245&nav=0Vixen quote on "Total capacity including Counterweights". Skywatcher (and Orion) do NOT include counterweights. eg: [from Skywatcher site] "for a load capacity of 20 kg (counterweight excluded)" As an example, the EQ6 carries 40lbs, yet the counterweights alone are 22lbs. If it included counterweights you would only be able to load on 18lbs. You need to check with each individual manufacturer whether they include the couterweights or not in the Payload capacity. Another thing to consider is where the counterweights are loaded. If you mount a counterweight a long way from the mount you may only need 1 small counterweight. Move the weight closer and you may need two weights to carry the same scope weight, so the amount of 'total' weight depends on location of counterweights. In other words, the further away you place the counterweight, the more weight you can put on the scope side. This site explains it really well: www.robincasady.com/Astro/WeightCalc.html
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Post by Deleted on Mar 28, 2014 14:59:43 GMT
It depends on the Manufacturer whether they include or exclude the counterweights in the 'Payload' specs. Celestron doesn't include counterweights. Celestron list their capacity is US Pounds as "instrument weight". www.celestron.com/c3/support3/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=2245&nav=0Vixen quote on "Total capacity including Counterweights". Skywatcher (and Orion) do NOT include counterweights. eg: [from Skywatcher site] "for a load capacity of 20 kg (counterweight excluded)" As an example, the EQ6 carries 40lbs, yet the counterweights alone are 22lbs. If it included counterweights you would only be able to load on 18lbs. You need to check with each individual manufacturer whether they include the couterweights or not in the Payload capacity. Another thing to consider is where the counterweights are loaded. If you mount a counterweight a long way from the mount you may only need 1 small counterweight. Move the weight closer and you may need two weights to carry the same scope weight, so the amount of 'total' weight depends on location of counterweights. In other words, the further away you place the counterweight, the more weight you can put on the scope side. This site explains it really well: www.robincasady.com/Astro/WeightCalc.htmlGood info Ken! I was unaware Vixen does things different. Good information to have!
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