elpajare
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home town/country: Girona-Spain
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Post by elpajare on Feb 22, 2019 12:23:18 GMT
Take out the reducer also...will affect exposition time.
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Post by Dragon Man on Feb 23, 2019 7:04:55 GMT
In my opinion the two photos are very overexposed. Look at the peak of the Histogram. I think it was Ken ( do you remember? can you recover this post?), a few years ago, who said that the peak should be shortly after starting the scale, to the left at no more than 30%. I remember that I was starting then and his article taught me a lot, thank you Ken. With the 200mm I do not exceed 18 "with the IMX224 and 20" with the IMX294 with the Gain to the maximum and dark skies. You have served 45 "! Try adjusting the exposure to the Histogram peak and leaving all parameters by default except White Balance
PD: Interesting the Histogram peak for each chip. Confirms the theory that 224 is more sensitive than 294 with equal exposure
You are welcome Carlos Yes, attempt to keep Histogram peak at the 1/3rd point (30-35%). As for using Gain, I rarely go above about 25% gain in any capture program or any camera. I sometimes raise Gain just to see what happens but I never like the results, so I stay in low Gain. If I want to clean the view up even further I use live stacking (average, not additive), but never more than 3 frames. The results are very pleasing.
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Post by Deleted on Feb 23, 2019 11:38:43 GMT
Not much success at all tonight. I took the FR out ,tried many combinations of exposures and gains. I could not get the histogram any further than about in the middle. The images were dimmer. I feel the FR is helpful. cheers Paul
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elpajare
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home town/country: Girona-Spain
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Post by elpajare on Feb 23, 2019 14:13:38 GMT
We have the same equipment, the only thing that varies is the software, I use Risingtech and you, I think, Sharpcap
Maybe the problem is to understand how Sharpcap works for good results. I do not know completely how this program works, maybe some partner could help you better.
But the control of the Histogram is basic and I only know one way:
Balance exposure and gain
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Post by Deleted on Feb 23, 2019 14:35:43 GMT
Yes Carlos. Same equipment and different results. I know what I have to do so I will keep working at it. I might give the C6 a go as I havent used it for a while. cheers paul
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Post by Deleted on Feb 25, 2019 11:46:39 GMT
The Rasa arrived back today. Unfortunately there is cloud about tonight after 5 crystal clear nights in a row. Managed to get a shot of ngc1365 and then tried the horsehead but too much cloud so I packed up Here is the 294 10"x 6. I dont see any evidence of mirror tilt... The second is the cropped
cheers Paul
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Post by Dragon Man on Feb 25, 2019 13:16:30 GMT
Wow Paul, if this is any indication, you are in for a treat!!! Look how sharp and tight the stars are. Despite cloud, you are off to a great start. Your image looks great
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elpajare
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Posts: 438
home town/country: Girona-Spain
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Post by elpajare on Feb 25, 2019 16:39:59 GMT
I like this combination of telescope / camera
The stars do not stain any light aberration and are punctual. It reminds me of a combination of RC + IMX294 that I use to photograph stars and clusters. But the 200mm RASA improves it. Mainly the detail in galaxies.
I am thinking of buying an RC of 8" more affordable in Europe than the RASA. What worries me the most is if they comes uncolimated easily, your experience will be of much use to me
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Post by Deleted on Feb 25, 2019 23:47:25 GMT
Thanks Ken and Carlos. I think a lot of Videoastronomers will be very interested in the mirror tilting. I am quietly confident that all will be well and I have a wonderful scope very suited to videoastronomy.
Mirror locking screws There are mirror locking screws on the back of the Rasa 8 which remain tight and are only altered by Celestron technicians . On the Rasa 11 they are knobs not screws which are loosened every time the focuser is altered by the astronomer or the scope is packed for travel. So the concept is totally different for the 2 scopes. There is no reference to mirror locks on the Rasa 8. The reason I know they are there is that when I tightened the screws the mirror rattle disappeared. I suspect one of the technicians at Celestron got this confused and loosened the mirror on a batch of Rasa 8's packed for travel. Mind you, I have no proof of this at all. When andysea posted on CN that he had exactly the same problem ,I started putting 2 and 2 together. The Rasa 14 is similar to the Rasa 8 and the mirror locks have been removed. jhayes_tucson who has been involved with the design of the Rasa 14 explained this on CN.
Carlos, the collimation screws are on what is called the lens group on the front of the Rasa which is the position of the secondary or the hyperstar on sct's. There are the usual 6 screws( 3 push,3 pull). Unlike the newtonians ,I should not need to alter these very often but they are there for the astronomer to alter if need be. I have had to alter the collimation on the hyperstar a couple of times. However, the mirror locking screws are for the technician only.
I am still curious why there have been so few references to the Rasa 8 on the forums.
cheers Paul
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Post by Deleted on Feb 26, 2019 10:58:48 GMT
Tried out the 178 and the 224 on the rasa. Not sure what happened with the 224. The stars were bloated so i will try that again tomorrow. Here is a 6sec x 10 stack with the 178, gain about 300 and bin 2 on sharpcap.
cheers Paul
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Post by Dragon Man on Feb 26, 2019 11:49:48 GMT
Paul, do you have to use Bin 2 because of light pollution? At Bin 1 your stars would be slightly smaller but you would need to expose longer.
Nice results so far.
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Post by Deleted on Feb 26, 2019 14:27:54 GMT
I was just seeing how low an exposure time I could go with the 178 using a camera that was not very sensitive. This was the 224 at 10s x 6. I was surprised by the bloated stars so figure I must have done something wrong and will try again tomorrow cheers Paul
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Post by Dragon Man on Feb 26, 2019 15:44:51 GMT
Looks like you left off the IR cut filter.
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Post by Deleted on Feb 27, 2019 2:43:04 GMT
Thanks Ken, but not the news I wanted to hear. I have so many uv/ir filters sitting around but none will fit the Rasa. Their light pollution filter is $349 cheers Paul
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Post by Dragon Man on Feb 27, 2019 3:42:28 GMT
Thanks Ken, but not the news I wanted to hear. I have so many uv/ir filters sitting around but none will fit the Rasa. Their light pollution filter is $349 cheers Paul Hmmmm . . . sounds like a commercial trick. Sell a fantastic scope, but only their accessories will fit it. Must be some way around it. Some clever fella will come up with an idea. $349 is just pure rip-off.
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Post by Dragon Man on Feb 27, 2019 4:06:55 GMT
Paul, I did a bit of reading and it seems that you can use other filters. It says all you have to do is remove the optical window from the scope. "Fig. 22: The RASA’s integral clear filter ensures optimal optical performance, it should be removed when using another filter in the light path. It can also be replaced with an optional light pollution filter which was developed in collaboration with Astrodon."Page 16 ---> HERE
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Post by Deleted on Feb 27, 2019 4:45:55 GMT
Thanks for the research Ken. Although the glass is 2 inch, its attachment is a different size than the standard 2 inch filters and there doesnt appear to be any way of removing one and inserting the other
cheers Paul
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Post by Dragon Man on Feb 27, 2019 4:48:04 GMT
Thanks for the research Ken. Although the glass is 2 inch, its attachment is a different size than the standard 2 inch filters and there doesnt appear to be any way of removing one and inserting the other
cheers Paul They have really made it hard.
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Post by Dragon Man on Mar 1, 2019 6:07:58 GMT
Paul, I watched a Video about an Aussie bloke with a RASA 8. It was an unboxing and showing how he sets it up, and in the Video he shows how the filter just floats around inside the housing (Weird) and if that is the case you can buy IR/UV cut filter glass without the housing and sit it in there, or remove the glass from your 2" IR/UV filter and use that (with a bit of electrical insulation tape around the edge of it so it doesn't chip or scratch).
Here's the bit in the video showing how almost any filter could just pop in there and float around:
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Post by Dragon Man on Mar 1, 2019 7:27:11 GMT
Paul, I read in CN that one RASA 8 user ordered the RASA 8 Light Pollution Filter because he believes he read somewhere (?) that the RASA LP filter has UV/IR cut coatings. I was curious as to whether this was true or not so I compared the RASA's cut-off points on the Spectrum compared to a true UV/IR cut filter (Astronomiks 'L' UV/IR Cut Filter). The results are Similar but no Cupie Doll. My findings show that the RASA LP filter still allows UV spillage but is quite good at the IR end. Here's the Technical Specifications Spectral graphs I used: The RASA LP Filter GraphThe UV/IR Cut filter graphBoth Graphs together for comparisonNotice the Spectral Wavelength points for UV and IR (UV from 300nm downwards, IR from 700nm upwards) From this, I believe that the RASA LP filter should be fine for IR reduction.
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