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MattJenko

6" RC progress report feedback please

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I am making some rather slow but steady progress with my 6" RC I think. Having gone a few iterations of various collimation processes, I think things are close enough that other considerations are now the ones that need addressing. I do not use a focal reducer, so this is native. I am struggling with focus, in terms of attempting autofocussing, where I think I keep getting step size and exposure time wrong and autofocus routines struggle with consistency. Maybe an up close and personal OC is not a good option, but I thought it would be.

Also, I have some tilt which needs addressing, but with such a tiny chip (Atik 414ex), I was hoping to dodge most of the curvature/title issues, but think those beasts needs confronting.

For those RC users out there - how do you guide? I am using an ST80 top mounted which has worked for refractors for me before, but a mirror based long FL system?

Another question to you all, a bit more philosophical. How do you know when you are approaching the best you can do, when you just have to admit that you can't do any more and maybe time would be best spent on something else?

M52 : 15 x 2 mins RGB. RC6, HEQ5, Atik 414ex. PixInsight.

 

M52_b.jpg

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Can't really help with advice, but I'm interested in one 6" RC myself so I'll follow this. You didn't use a focal reducer because you didn't want to or you don't own one? If I get one, I'll have no interest in imaging at its native focal length.

There's a topic started by @johnrt

He has some very nice results with this scope.

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Thanks, been mightily impressed by John's work with his. I do have one of the CCDT67 reducer/flatteners, but don't fancy using it with this particular scope. I have other setups which hit the focal length that would give me, and I am more interested in 1m+ imaging with this one. Also, I am saving up for a high res spectroscope, which will end up on this scope for starters and yet more learning, so want to master it as a full mirror system first.

I do think it has a lot of potential for all kinds of imaging uses, just find the amount of time I get to spend trying things out to be limited, with health and other circumstances, so hoping to get some tips on pushing the pace of improvement :)

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General recommendation - use very large chip to fix issues with collimation and tilt. Very large chip easily shows where the problem is.

This is what I do: center star on sensor and get best focus, move to each corner and monitor how focus is changing. Granted, I do have Cmos sensor and use SharpCap for all of this, so it is quite fast to get readings in each corner (either Bahtinov mask or star FWHM).

2 hours ago, MattJenko said:

For those RC users out there - how do you guide? I am using an ST80 top mounted which has worked for refractors for me before, but a mirror based long FL system?

OAG with my RC8"

2 hours ago, MattJenko said:

Another question to you all, a bit more philosophical. How do you know when you are approaching the best you can do, when you just have to admit that you can't do any more and maybe time would be best spent on something else?

When it is perfect :D, or when I have very good understanding of why, under given circumstances, that is about as good as it will ever get.

I was fixated on getting better and better guiding, hoping to pull of some strange miracle of having 0.2-0.3" RMS with HEQ5. But after much reading on mount performance in general I realized that 0.5" RMS is about the best I'll ever get - and this is on a good night :D.

 

 

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G'day Matt,

I found on my 6"RC the tilt correction was something I needed to address before I was 100% happy with the output from the scope. The corrector rings aren't too expensive, and are easy to fit & work with.

A good old fashioned ST80 guider set up works really well on these scopes as they have the top rail you can just clamp on to, I have an Altair clamp that I attached the scope rings to. An off axis guider would also work well. I tried one but got frustrated with setting it up and went back to the ST80, which just works without hassle.

Your last question - well no image is ever finished, you can *always* add a little (or a lot) more depending on how you feel. The longer I have been imaging the more I have wanted to invest in single images.

Edited by johnrt

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I have an Altair RC8" and can fully understand where you are coming from with regards to focus.

Sometimes I feel it is off and other times good, on my last clear nights session I started using Astro Photo Tools for focusing and what a revelation on getting things sharp, especially since I can focus remotely in the warmth of my study using the Moonlite focuser that I fitted, if you don't have Astro Photo tools then give it a try, I think you'll be surprised. http://www.ideiki.com/astro/Default.aspx

I too use an ST80 on my RC, works really well top mounted and is nicely balanced with the RC.

HTH.

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Thanks all. Had a decent session with it after the original post and things looking pretty ok, although I manually focused with a mask. ST80s rock. Might not need a tilt adaptor with my tiny 414ex. Probably would with a larger chip.

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