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Hi! I'm a noob with an RC6 and I have some questions that are not "how do I fix my totally messed up collimation?"

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#1 dx_ron

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Posted 22 July 2021 - 02:49 PM

(I'm not a total noob, I have been imaging with my Z61 refractor for ~8 months now)

 

I just came in to possession of what seems to be a fairly new iOptron RC6. Purchased from an older gentleman who had recently given up hauling around his 12" dob. He tried the RC6 but fairly quickly decided it was not the visual scope he was looking for and put it up for sale. It arrived at my house in seemingly excellent shape with still a hint of new-telescope smell, even.

 

1. - Just a bit about collimation: Having read most of the collimation nightmare stories and waded through many posts about potential procedures and gadgets, I was convinced to wait and look at stars before loading up on gadgets to try any indoor collimation. I am totally a novice at looking at defocused stars, but I think it actually looked pretty good (yeah! if true). I used Vega (probably more like a 2nd mag star last night thanks to haze and smoke) and a 9mm plossel eyepiece. After finding focus (all of the extensions) all I really knew to do was center the star, defocus inward and see what it looked like. Despite fully expecting to see ovals, the black center looked quite respectably centered in respectably round diffractions. On the downside, it was very inconvenient and uncomfortable to do this - basically laying on the driveway propped partway up on an elbow and twisting my neck to get at the eyepiece. Next clear-ish evening I can try with the tripod slightly less extended to see if I can reduce the "propping partway up" part to be able to have more time with my head held still.

 

Is there more I should be checking visually? Or just wait until I can hook up a camera?

 

 

 

2. - Stuff I need to hook up a camera: Obviously a 2" compression to M42 (M48?) adapter. Will that be called a prime focus adapter? I always used the refractor with the screw-on flattener, so I don't own a suitable adapter to get from the compression fitting to the camera. With no reducer, I will expect to find focus with fewer extension tubes, rather than more? For actual AP I will purchase a CCDT67.

 

3. - Guiding. I am well aware that my CEM25P might not be up to the task, but there's only one way to find out. I have spent a fair bit of effort tuning the mount and consistently achieve at or better than 0.75" RMS guiding, but the only way to know if it is capable of sub-arcsecond guiding with the RC6 is to try it.

 

Plan is to buy an OAG. I would be happy to move to guiding the refractor with an OAG anyway, even if it's not necessary. Balancing the clunky 50mm guidescope has always been a challenge. Is there a reason to go with one OAG vs another (Orion TOAG / ZWO / QHY)? I will be needing 85-ish mm backfocus from the reducer, so I don't think width of an OAG will be a limiting factor.

 

I know the 120mini is not the best guide camera for an OAG, but I have it and might as well use it unless it proves to be inadequate. It seems a fair number of people get by with a 120mini for at least a while.

 

*IF* this all actually works, I will strongly consider buying a Moonlite focuser, but that can wait. I'm not in a huge hurry and will continue imaging with the refractor.

 

4. - Yes, I know a 183 is the wrong sensor for even a reduced RC6, but I'm not going to worry about swapping cameras until I determine that I can or cannot reasonably guide the RC6.

 

Hopefully I can learn something from asking these questions - I'm all ears.


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#2 MikeECha

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Posted 22 July 2021 - 03:39 PM

I have had my AT6RC for about a year or so. I bought it to experiment and see if like long fl and if I wanted to buy a larger one.

Collimation is not a mistery but the lack of good way to handle the secondary with the accuracy it requires can make it very frustrating unless you enjoy tinkering with things more than imaging.

My suggestion would be to not touch collimation until you have the cam. And then read about all the issues and try to fix them before collimation.
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#3 dx_ron

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Posted 22 July 2021 - 04:17 PM

Not planning to touch the adjustment screws at least until I have the cam hooked up. No current plans to go with anything beyond the DSI approach, as I am becoming convinced by the arguments that bench collimation is more likely to do harm than good unless the scope is known to be substantially out of whack.

 

In fact, I am now cautiously optimistic that I have one of those RC6s with "good from the factory - don't touch it" collimations. But I wonder if there is more I can do visually - not to start adjusting but to get a better sense for how close or not so close the scope is to good collimation.



#4 MikeECha

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Posted 22 July 2021 - 04:44 PM

I have not tried to adjust visually but I know how little it takes to mess it all up in real time with life view. So visual is out of the question for me. The diffraction patterns are very difficult to read accurately and the seeing just makes it close to impossible for me. By the time I realize I am going the wrong way things are already really bad.

 

Wait for the camera and take a single picture like the DSI method. You will know right then and there. You will not believe how sensitive that secondary is.



#5 licho52

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Posted 22 July 2021 - 11:53 PM

My 6" RC was a stepping stone to my new 8"...great scopes for the price.  I also have a 61 for wide fields but when you want to go deep there the RC.


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#6 dx_ron

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Posted 24 July 2021 - 10:42 AM

I started to attach the 183C last night, but it turned out I had done something horrible to the focuser. The draw tube could be either locked or slide freely, no in-between and no control by the knobs. I already had the mount set up, so I just went ahead and did a bit of manual rough-focus observing, smoke, moon, light pollution and all. Even very low in the sky through all the smokey atmosphere and right next to the moon, Saturn at opposition at 150x was enough of a treat for the wife and kid. (astrophotographer's wife quote "it's nice to actually see something through your telescope")

 

This morning I figured the focuser out as I was prepping to dismantle it. Apparently I had at some point fully loosened both the tension and lock knobs and the drawtube had gotten badly misaligned. All better now, and I am now one of the only people on this forum to be grateful to have a stock GSO focuser smile.gif (for now). We'll see if there are enough clear skies tonight to get a focused (for f/l astrometry) and de-focused photo of a nice star field.


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#7 MikeECha

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Posted 24 July 2021 - 01:09 PM

I started to attach the 183C last night, but it turned out I had done something horrible to the focuser. The draw tube could be either locked or slide freely, no in-between and no control by the knobs. I already had the mount set up, so I just went ahead and did a bit of manual rough-focus observing, smoke, moon, light pollution and all. Even very low in the sky through all the smokey atmosphere and right next to the moon, Saturn at opposition at 150x was enough of a treat for the wife and kid. (astrophotographer's wife quote "it's nice to actually see something through your telescope")

 

This morning I figured the focuser out as I was prepping to dismantle it. Apparently I had at some point fully loosened both the tension and lock knobs and the drawtube had gotten badly misaligned. All better now, and I am now one of the only people on this forum to be grateful to have a stock GSO focuser smile.gif (for now). We'll see if there are enough clear skies tonight to get a focused (for f/l astrometry) and de-focused photo of a nice star field.

Glad you got it figured out. 

 

You are not the only one who likes GSO focuser. Me too. Specially for thee price. I have one on my AT6RC and bought another GSO for a used C8 that I plan on de-forking for AP after the planets go away this year.

 

NINA (software) is happy focusing with a step size of 60 and a backlash of 65. With that I get R^2= 95 and above all the time.




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