Hi all, The autoguiding battle continues... It seems that the QHY-5 runs out of back focus, how much back focus? im guessing 1 extra inch!
Has anyone else experienced this using a OAG?
my question is, Should i source a longer nose tube for the QHY-5, or should I get a tube extender?, or should i purchase a Celestron T adapter which looks to be 20mm longer than the bintel one i am currently using?.
BINTEL http://www.bintel.com.au/Astrophotog...oductview.aspx
My thoughts are (please correct me if im wrong) but adding a longer T adapter to my imaging train, will decrease the back focus required to bring the QHY-5 into focus?
I am having the opposite problem at f4 - same answer though. As Marc says, if the main camera is in focus, the guide cam will be as well if the distances to the 2 focal planes are the same. Just looking at your setup picture, provided the main camera focuses, you need to put a fair bit of an extension into the QHY side to push that focal plane further out. anything that you change in front of the OAG will not fix the problem.
Easyest way to test what you need to do is to focus the camera roughly and then move focus out or in until the guide camera focuses. If you need to move the main camera futher out to focus the guide cam then the guider needs an extension if you need to move the main camera inwards then the guider needs to be closer to the oag.
James, two nights? Sorry, but thats nothing. I've spent three months optimising a fully automated system. Patience is a big part of this game, and the advice given above should help you.
Some people do not realise the difficulty involved in just finding a star in the field of a OAG. Remember it is much smaller than your primary FOV. Make sure to slew to a densely populated star field, this will certainly help.
James, two nights? Sorry, but thats nothing. I've spent three months optimising a fully automated system. Patience is a big part of this game, and the advice given above should help you.
Some people do not realise the difficulty involved in just finding a star in the field of a OAG. Remember it is much smaller than your primary FOV. Make sure to slew to a densely populated star field, this will certainly help.
Good luck,
Steve
Thanks Steve but im not trying to optimize an automated observatory, just a OAG, if you wish to spend 3 months setting up an automation, more power to you. But for me 2 perfectly clear nights wasted, and 12 hours of pulling my hair out over a $170 OAG + QHY5 is about the limitations of my patience. Especially when the QHY5 has no instruction on focus, and the OAG has very little information at all, not one salesman at any stage in the purchasing of these items has said "Hey have you got a extension tube? you should probably get one is will save you hours of stuffing around and it only costs $30", I would have paid ten times that if it would save me the frustrations of the past few nights.
Because i live in the middle of whoop whoop, all post takes between 5-7 days, so everytime i hit a snag its another 7 days before i can rectify it!!, im into the 2nd week of owning the OAG and Cam, and still it hasnt been used as intended..
I am very sure once all the dramas are sorted, i can then learn to use the radial functions to find a bright enough star to guide on, then I can enjoy my many hours of astronomical joy. (which i have patience for)
Thank you everyone for your advice, now just have to wait a week to try them I have a great daytime target, a mobile phone tower on a mountain 10 kms away, i used it to align my finder.
James,
Setting up during the day on a distant object is definately the way to go...
Each camera/ guider is different and requires a different solution - the supplier(s) honestly don't know how you're going to use the equipment - that's something you need to appreciate.
As mentioned - the back focus to the imaging camera is the same as the spacing to the guide camera.....
Ok i got the extension tube and tried a daytime focus, it now seems i have too much back focus LOL!! I will butcher a cheap 6mm plossl tomorrow and see if i can mcgyver a shorter extension tube. if all goes to plan, I will measure it and borrow a friends lathe to build a custom extender.
If i still have no joy i may scrap the OAG idea and go with a guide scope.
I had no end to problems trying to get focus with an Orion SSAG with an OAG. I ended up selling it and went back to guidescope style instead (STILL refining that!)
From that picture alone, I can see that the distance from pick-off prism to SLR chip is greater than the distance from pick-off prism to QHY chip. Easy fix, buy 1 or 2 1.25" little extension tubes from bintel/GSO. Threads on end of QHY 1.25" nose piece and extends it.
A mate has the $800.00 USD MMOAG ftom Astrodon. Works a treat, round stars on guider chip, easy to adjust. He was up and running in 24hrs. Having owned and sold the Orion Deluxe Off-axis Guider, you certainly get what you pay for...
Ok, the next problem is that the back focus is 2mm above the end of the guide port, im going to have to get creative here, or extend the imaging train behind the guider so that i have a little extra focus to play with while using the 50mm extension tube on the guide port. (SEE ATTACHED DODGY PAINT DRAWING)
Just checking, during daytime testing, you are bumping QHY exposure setting down from 99 to 1 or so?
Indeed i am, i could see a very blurry tree when i was checking the focus, it just looked like a black blob. I was using the QYvideo program as i found the live feed easier to get focus.
The good news....it can be done!
I've used a QHY5, ATiK16 and now a Starlight Lodestar guide camera to guide my spectroscopes on C9.25 and now the C11.
I use a beamsplitter, but it has the same off axis issues as a conventional OAG....
As long as you remember the imaging camera and the guide camera maust be at the same distance...you can alter each to get the best outcome....
When you get there, you'll wonder what the fuss was all about!
Losing battle with an autoguider
