6" RC for Galaxy season

[nightster]

I've been wanted a longer FL for a while. Now that I'm competent with my wide 80 frac it's time for another challenge. My budget only allows for the 6" version. With a FL of 1370mm and my Atik 460 it puts my pixel scale down to .68"/px. I and wondering how this will change my approach to imaging.  

I am also investigating if my MoonLite w/ stepper will work on this scope. I also plan to use the same flattener (Stellarvue SFFR6.) 

Curious on any thought people have on moving to one of these scope.

[ronin]

Nothing direct but if you are in a club or want to find/join one then ask if others in it have experience of an RC.

They are good but I read as many (maybe more) cases of people being unsuccessful with them as I see people who manage to get results. Seems you either can work with one or cannot and not much in the middle.

Someone recently had simply given up with theirs, may have been someone in the US. Think it was to be a case of "Free to good home" or immense pleasure in taking a big hammer to it.

[johnrt]

Well they are not for the faint of heart. The issue appears to be for most getting them collimated, but once they are up and running you can just forget messing with them and get on with it. 

Check out my webpage (link in sig) to see my images with my 5 year old 6" RC. I use the APCCDT67 reducer and Atik 460ex. 

[nightster]

Thanks @johnrt. That's what I was looking for. Really nice results. 

[ollypenrice]

0.68"PP is a big (a very big) ask. I've worked at 0.66 in conjunction with Yves and his 14 inch Dall Kirkham. We were mounted on a Mesu 200 with excellent tracking under autoguiding. Even so, I'm not convinced that we were really acheiving the theoretical resolution. (We had intended to do a lot of binned imaging but the camera wouldn't bin properly.)

You can still get a good result even if you can't actually realize 0.68 but, given that the RC can be difficult to collimate and that a coarser sampling rate might still have you at the limit of the guiding and seeing, you might consider the alternative of a slightly shorter FL in an easier optical system. Just a thought.

If you got results like John's you'd be a very happy bunny but not everyone does!

Olly

[nightster]

I was most concerned of the pixel scale and I'm glad @ollypenrice mentioned that. The problem is during this season I have almost no options at 480FL. Sure Mak chain, couple others. Even the clusters are small in my FOV. My camera does Bin2 quite nicely.  I'll have to try to calcuate the pix scale for a binned sensor. Or is there a website that does that?

[ollypenrice]

16 minutes ago, nightster said:

I was most concerned of the pixel scale and I'm glad @ollypenrice mentioned that. The problem is during this season I have almost no options at 480FL. Sure Mak chain, couple others. Even the clusters are small in my FOV. My camera does Bin2 quite nicely.  I'll have to try to calcuate the pix scale for a binned sensor. Or is there a website that does that?

There are several. Voila!

http://www.12dstring.me.uk/fovcalc.php

http://celestialwonders.com/tools/imageScaleCalc.html

Olly

[Anne S]

2 hours ago, nightster said:

I was most concerned of the pixel scale and I'm glad @ollypenrice mentioned that. The problem is during this season I have almost no options at 480FL. Sure Mak chain, couple others. Even the clusters are small in my FOV. My camera does Bin2 quite nicely.  I'll have to try to calcuate the pix scale for a binned sensor. Or is there a website that does that?

I've got a SX H694 which is the same chip as you. I've also got the same scope you're planning to get. I took the attached with a 0.6 reducer on with the pixels binned 2x2. That gave me 2.3PP. Without the reducer I'd get 1.4PP which is the same as my 102 triplet. I think this scope will be excellent for galaxies, planetary nebula etc.

Forgot to say I got the image scale figures from the Atik camera app. It lists their cameras and you can add your own scopes.

Anne

[johnrt]

Olly makes a good point about the pixel scale. I have the same camera a 460ex, and reduced by x0.7 with the CCDT67 it produces a well corrected field & a pixel scale of just under 1 arcsec/pixel (0.97 for the Statto's). My mount, an AZEQ6, guides at around 0.67 arcsec error, so I'm actually imaging a little under the guiding capability of my kit, and achieving a resolution under what it could be on paper.

But, get one of these bad boys up and running and they purr away, show me a colour corrected triplet refractor at 900mm / f/6 that means I don't have to sell my car and walk to work everyday and I'll gladly swap my RC for one. You can't!

From earlier this week.....

 

[nightster]

And here it is ready for first light. I need to do some calculations to determine a good starting step size for autofocus and add the new hardware into SGP's profile wiz. And being a generic GSO it is missing some sort of Logo on the tube. I suppose a nice decal would look fun and possible create questions at my clubs obsy's. I'm thinking a HHGTTG '42' or a blue police box.....

[nightster]

Successful test night. I was able to come to focus with a single 1" GSO spacer. Though the 1.5" drawtube was racked out most of the way. I may end up using the 2" spacer and keep the drawtube a bit. I did a rough collimation with a Cheshire, but there is some more mirror collimation necessary as I can see star shape aberrations.  I was happy with how this FL guided.  I was able to take flats with a LED dimmable tracing box I picked up from amazon for 50$. I am really excited to stretch the legs on this baby RC.  A whole new batch of targets just became worthwhile to attempt.

M92 20x120s RGB  

 

[nightster]

@johnrt can you tell me how you collimate yours?

[johnrt]

2 hours ago, nightster said:

@johnrt can you tell me how you collimate yours?

I just use a good old fashioned Cheshire eyepiece. A star test on a defocused star after the Cheshire is then a really good way of testing and perfecting the alignment of the mirrors.

[nightster]

1 hour ago, johnrt said:

I just use a good old fashioned Cheshire eyepiece. A star test on a defocused star after the Cheshire is then a really good way of testing and perfecting the alignment of the mirrors.

Yes, that seems to be what I've read is best practice. But How? Do you use the scope visually and star test? Or can you use the CCD?  As I was slowing moving into focus last night I had donuts but couldn't really discern concentric circles on either side of focus.  I was not on a bright alignment star, maybe that was the problem. Any insight would be helpful.  

[johnrt]

13 hours ago, nightster said:

Yes, that seems to be what I've read is best practice. But How? Do you use the scope visually and star test? Or can you use the CCD?  As I was slowing moving into focus last night I had donuts but couldn't really discern concentric circles on either side of focus.  I was not on a bright alignment star, maybe that was the problem. Any insight would be helpful.  

Yes, use the CCD to star test, and I would also reccomend CCD Inspector to assist you on the final tweak. My Cheshire gets me close enough to not have to worry too much about having to star test, but others I have spoken to have found the need to.

Select a nice bright star preferably high up near zeneth so aid with the seeing.

[nightster]

What I found difficult with the  cheshire is that the target is very small and making the minute movement showed no change until it went too far. I am wondering if it's possible to add a cam to the cheshire that would allow for a zoom and possibly for a bullseye overlay that could help with the alignment.  Ive seen the Webcam attached to a lens cap and the use of Mirren de Collimation. In the end it is going to be the star test. I am going to try to make an artificial star so I don't need to drag everything outside for a real star.

[nightster]

Well it works. I hot glued a HD webcam to the pinhole on the Cheshire and a bit of Sharpcap tuning I was able to see the a bit of light on one side (at 1 o'clock) of the center dot. I tuned it till it was centered.  My artificial star wouldn't come to focus so I'll have to use the real thing.  But here are some snips of the experiment.  

[johnrt]

13 minutes ago, nightster said:

Well it works. I hot glued a HD webcam to the pinhole on the Cheshire and a bit of Sharpcap tuning I was able to see the a bit of light on one side (at 1 o'clock) of the center dot. I tuned it till it was centered.  My artificial star wouldn't come to focus so I'll have to use the real thing.  But here are some snips of the experiment.  

Heheh, very ingenious, I wonder why nobody has ever made an adapter to do exactly this? You could sit and collimate in real time just watching the screen and adjusting the hex bolts!

[nightster]

1 minute ago, johnrt said:

Heheh, very ingenious, I wonder why nobody has ever made an adapter to do exactly this? You could sit and collimate in real time just watching the screen and adjusting the hex bolts!

It was simple. I'm at the business end of the scope looking at the screen. I make a tiny turn on a hex wrench, and I see the mirror move. The other part that helped was I could see my hand in the image thus I KNEW which bolts needed to turn which direction. No guessing.  What is needed is a Cheshire that has T thread machined into it's outer tube, down at the pinhole end. That way, a simple T2 to C mount adapter and a cheap Cmount CCTV lens would attach to the front of my Lodestar. Unthread it and you use the Cheshire visually. Thread it up for fine tuning in Sharpcap.

 

 

[nightster]

I was able to get a few star test images. I had to shut her down early, its a work night. But here are two images from Inside and Outside of focus. Only the camera in the image train.  I made no adjustments just grabbed the frames to get an idea what people think should be my next move.

 

[Dave In Vermont]

Very nice work!

I actually enjoy collimation, I might just do similar to what you have.

Thanks for the idea -

Dave

[nightster]

It was a shame the such a nice little scope didn't have a single mark, logo or brand on it.  So I added one. 

[nightster]

And in order to keep my mini RC6 blog up to date I also figured out a case for this guy.  It does bother me that the GSO made scope never have case options. Same with my AT6IN I put it in a locker box. This box fell off a truck and I happen to find it. I needed modify the interior a bit to make it fit and I'll need to add some more foam to the bottom and side but it fits