2 Star Alignment with DSLR

RKenning (Robert) · #1 03-01-2016, 07:27 AM

I have had a few good viewing sessions with my Advanced VX mount and BD ED80 scope. I have the setup and balance working well and getting good polar alignment and accurate tracking. I have finally got my Nikon D90 set up and attached to the ED80 and then realised that the camera setup with balance requires another rebalance with shifting of the counterweight and OTA. Of course, all my previous alignment setup with the EP and diagonal goes out the window. So, my question is, how do I do a two-star alignment, including calibration stars, with the DSLR attached? Another issue I came across was with the focuser. It doesn't like racking in and out with the DSLR attached and there is slippage. I have been assisting the focuser by taking some of the camera weight when racking in but I feel like the whole system is being stressed out with the excess weight. I'm just wondering how other folks manage with a similar setup? Thanks for any advice. Clear skies. Rob

Rigel003 (Graeme) · #2 03-01-2016, 10:09 AM

When you polar align, you are aligning the mounting, not the scope with any particular accessories. Once the mount is accurately aligned to the pole, anything attached to to it, at any angle, will follow the stars accurately. So changing counterweight for your camera and rebalancing the scope after alignment shouldn't have any effect.

RKenning (Robert) · #3 03-01-2016, 11:10 AM

Thanks for your advice in that Graeme. I realise that the polar alignment won't change by removing the diagonal and reticle eyepiece and replacing with the camera and adapter tube, unlock clamps and rebalance, but how do I do a two-star alignment when I don't have an eyepiece or illuminated reticle to centre the stars and hit align on the handset? Do people use 'Live View' on the DSLR and centre the stars or the viewfinder?

madwayne (Wayne) · #4 03-01-2016, 04:18 PM

Hi Robert - what you're looking for is called a flip mirror. On the straight through path you have your camera. And when the mirror is flipped, like a diagonal, your illuminated eyepiece is on top. Don't forget to unflip the mirror before you start photographing otherwise you'll end up with your darks before your lights 😀.

Wayne

Merlin66 (Ken) · #5 03-01-2016, 04:27 PM

Robert,
I use the stock standard focuser on the ED80 with various cameras including DSLR......check the adjustment screws...should handle a DSLR OK.

I have an electronic finder I rigged up with an ol' 200mm Zuiko lens and an ATiK16 camera. I can then use the FOV to sync alignments. A good solution for me...
The flip mirror idea is a usable solution if you have the 60mm backfocus space available.

rogerco (Roger) · #6 03-01-2016, 05:45 PM

After you do your alignment with the eyepiece, as long as you don't slip the clutches or turn off the tracking you don't need to redo the two/ three star alignment again.

If your camera has live view however you should be able to do the alignment providing the camera has a grid you can superimpose on the display

barx1963 (Malcolm) · #7 03-01-2016, 05:48 PM

With the alignment and balancing after setting up i went through the same issue.
Simple solution was that the only thing that changed for me was instead of a camera and an extension tube, when doing my initial alignment I had a diagonal and eyepiece, which was only a little bit lighter than the camera anyway. So I just balanced everything with the camera etc in place and racked out the focuser to within a mm of correct distance. Then did the balance and just swapped the EP and diagonal in. Still worked perfectly well.
I only do my initial 2 star alignment and first polar alignment using the Synscan routine using the eyepiece. After that I just use the cameras, phd and my auto guider to refine the PA and liveview from the camera in BYE to do final 3 star alignment. Using a simple red dot finder allows me to make gross adjustments in the pointing sufficient to get a star showing on live view.

If you don't want to use BYE (I think there is a Nikon version now see here http://www.otelescope.com/index.php?...emium-edition/ ) just using liveview can also work although an articulated screen helps!

Malcolm

RKenning (Robert) · #8 03-01-2016, 07:30 PM

Thanks to all for your advice. I will try to do a 2-star alignment with the camera in live view and see how I go. If that doesn't work I will use the EP and diagonal and then insert camera and rebalance on the fly. I have marked the dovetail and counterweight bar as per the DSLR combo so providing I'm careful I should be able to make the adjustments. The flip mirror sounds good, I might look into that. I think I might need a focal reducer as well but I haven't run the above setup yet because I got caught with clouds rolling in at sunset. As for the focuser, it has 8 fine black hex screws on the bottom as well as the chrome knurled clamp bolt. Do the fine screws need to be adjusted (tightened)to stop the slippage? Thanks to everyone for your advice.

madwayne (Wayne) · #9 03-01-2016, 08:16 PM

You're welcome on the flip mirror, Bintel would have them in stock I would reckon. Take a photo of your focusser, on my ED80 the tension is adjusted by a thumb screw not little screws as you describe.

Wayne

RKenning (Robert) · #10 04-01-2016, 12:38 PM

I had a fairly good session last night( 10 pm till 4:30 am)with the Nikon D5300 attached to the end of the ED80. I managed to do a few 2 star-3 calib star aligns through the night, using the camera, as more stars came into view from behind the towering gum trees. I took 60 shots, with the first few being overexposed and blurred. I settled on 1600 iso and 20sec exposures which gave me good results. The north sky and Adelaide glow made me wind back the exposure a bit to counter the orange sky background. Throughout the session I checked the focus with live view and the zoom in function, which worked quite well. I might look at a flip mirror down the track, but the 9 oz weight added to the end of the OTA is a bit of a concern. I already have my Sigma 150-500 zoom parked on top of the scope towards the front to counter the weight of the camera, as a temporary measure. I might fabricate an aluminium counterweight rail to attach to the piggy-back bar that I can slide some weights onto. Anyway, it's all good for now and I'm looking forward to getting out to a clear site for a few sessions.
I wish everyone clear skies and good hunting. Cheers - Rob

Howard (Howard) · #11 07-01-2016, 11:06 PM

Hey Robert. RE doing alignment with a camera instead of an eyepiece ...
1. If you have the camera connected to a pc then the IIS download pages has a software reticule window app which goes semi transparent. Overlay its window over the liveview window and bingo you have a reticule on the pc. Under IIS, Resources, Files see Als Reticule
2. If you dont have a pc in the field and are just looking at the lcd back screen on the camera, stay unzoomed until you get the alignment star appearing on the camera lcd screen. Then centre as best you can and then zoom in (Canons get to 10x zoom ... dunno about Nikons). When at highest zoom, defocus the star. You can centre a big blob far easier than a sharp pinpoint.
3. After pressing ENTER to register that star for your first alignment point, refocus before unzooming and before moving to the second alignment star. Easy way is stay zoomed and adjust focus until you judge the star in the zoomed mode is as small as you can make it.
Cheers
Howie

RKenning (Robert) · #12 08-01-2016, 09:21 AM

Hi Howard. Thanks for the tips on the reticle app. I do get a 1 cm red square in live view on the D5300 and I can zoom in pretty well, but find the pin prick of white is fairly easy to centre, however, I will give the defocus method a go and see how I fare. I haven't got the camera tethered yet, I have Nikon Camera control on the PC but haven't played with it yet. I will need to use a USB hub as I'm running out of ports on the PC.
Using the 'live view', I did manage a pretty good alignment by doing a 2 star and one calib star then switching to polar align and used a bright start with the required manual az and alt adjustments. Taking 20-second shots resulted in pin sharp stars. I'm hoping to repeat that process again tonight, cloud gods willing.
Cheers -Rob

Camelopardalis (Dunk) · #13 08-01-2016, 10:05 AM

Robert, many DSLRs have a live view grid option...have a look in one of the menus on the camera for it. If you enable it, it should give you an overlay. Some even give you a choice of grids! Then use the +/- buttons in live view to help centre the star on the screen. So long as you get the alignment stars more or less in the same place on the screen each time you should get good gotos.

RKenning (Robert) · #14 08-01-2016, 11:32 AM

Hi Dunk. After a bit of button pushing I found the grid option. You have to be in Live View then press the i button next to shutter and cycle through the options but it ends up with red rectangle and white grid overlay. That will prove very useful when it's dark. I have just bought a Hahnel intervalometer today so it should be a fun night tonight.

Camelopardalis (Dunk) · #15 08-01-2016, 07:56 PM

Cool, glad you found it! Each DSLR (brand) is different, so it take some button pushing