Widefield Triple Imaging Rig

[Gina]

Good news Now running all three cameras in three separate instances of Artemis Capture. I connected all 3 cameras and rebooted the laptop. Then ran Artemis and it listed 3 cameras 314L+ 1xxxxx, 314L+ 2yyyyy and ArtemisHST the latter being the 460EX. The figures fro the 314L+ caneras I presume are serial numbers. I chose the 460 first then ran Artemis twice more. 2nd run gave choice of 2 cameras - the 2 314L+s so I chose the serial 1xxxx. 3rd run initially came up with "could not find camera" but came to life a bit later. I set up separate folders for each camera and then enabled saving. Now I have a great big pile of files in each folder

[Gina]

Here are 3 images, one from each camera all taken around 9:35, converted to TIFF in FITS Liberator, stretched to same brightness in Ps, resized and saved as PNG.

Slight misalignment and also the 460 is slightly out in rotation. All lenses are set at infinity focus so since the focus is at a few hundred yards rather than infinity, the lens mountings will want a little bit of padding out - I suspected that and provided for it.

[sloz1664]

Hi Gina,

Hurdle one accomplished albeit a little tweaking.

Love this thread...

cheers

Steve

[Gina]

Another three with the 460EX lined up with the others.

[Gina]

Except that I processed the wrong file Tyring again

[Chris]

Rotations looking better, getting close!

[Gina]

Hi Gina,

Hurdle one accomplished albeit a little tweaking.

Love this thread...

cheers

Steve

Thank you Steve

[Gina]

I can move the lens mountings to line up the images but ATM this is just manual by slackening the screws and sliding - a very coarse adjustment

considering the pixel size of the 314L+. Here is the result of my attempt to match 460 and 314 sizes and rotation, combine as RGB in Ps then slide the images to match as well as I can. Much to do yet!

[Chris]

Well look on he bright side Gina you've managed to produce a picture of the veil nebula using 3 terrestrial pictures

[Gina]

I've put some spacers in the lens mountings so hopefully I'll be able to obtain focus on stars. The reason for the misalignment of images is poor production control on the holes the lens adaptors fitted in. They came out a bit bigger than I had intended. There is around half a millimetre of slack. That works out at about 75 pixels. I'll try to get the lens holders central in their holes and see if that's any better. Who knows, the weather might just let me test this on the stars tonight, then I can run the images through RegiStar

[Gina]

Another try after the dismantling and reassembly - not a lot better though.

[Gina]

Had another go at lining up the images in Ps by adjusting the size of the 460 image (green) to match the 314 ones and then moving the colours to line up. Here is the result.

There was quite a strong wind and the tree in blossom in the foreground was waving about in the breeze and would only line up if the exposures were virtually exactly at the same time - which they weren't. The camera angles are almost perfectly matched - I haven't applied any image rotation this time. One of the 314L+ images is still off to one side though (but not quite as much as before). I shall have to have a think about how to fix this.

[Gina]

Had some clear sky between patches of cloud last night and was able to do a test run on the stars. Lined up on the Cygnus Loop (where the sky was clear, adjusted focus on each lens, apertures set to f4 and ran 60s subs with binning 3x3 on green (460EX) and 2x2 on red and blue (314L+). Yes, still using RGB filters (of course NB would be likely to give a better image but I wanted similar brightness on all three images for this test). With a 135mm on the 460EX and 105mm on the 314L+s the coverage was greater on the 460EX and it well covered the other frames. With these short exposures I didn't bother with guiding.

Here is the combined colour image. Each colour stacked in DSS, stretched in Ps, images aligned with RegiStar then conbining and final processing in Ps. This is the full uncropped image showing the coverage of each lens/camera combination.

So with this set of lenses it will be helpful to align the 314L+ images as well as possible but these will easily fit within the 460EX frame.

[Gina]

And here a cropped version with further colour and contrast boosting in Ps.

[JohnC64]

That's looking pretty impressive there Gina. With your latest physical alignment and with some help from registar to perfect the star alignment it looks like you are onto a winner here.

Nice one

John

[Gina]

Thank you John

[ollypenrice]

I use lenses and just do it manually with a small bahtinov mask. I just have Artemis on repeat and select just a small box around the star. Helps if you can see the screen at the same time though.

I'd be perfectly glad to be proved wrong but I very much doubt that you'll be getting the best out of your lenses this way. When I used a TS microfucuser on my Canon 200L I found I could get far lower FWHM figures than I could by handling the focus ring directly. While I perfer to have as few electronic bits as possible, personally, I agree with Gina that fine focus is remarkably critical.

I would have thought that the tolerance or intolerance of a system with regard to focus would depend on the pixel size and the F ratio. Big pixels will stay 'sub pixel' in error for longer than small ones and steep light cones have shallower depths of field. No?

Olly

[Gina]

I have a plan for adjusting the framing by moving the camera(s) and have ordered some 1.5mm thick aluminium plates. I'll see if I can produce a diagram. Looks like Friday may be the next time I can do some night-time testing but with the weather things may change before then

[Gina]

I'd be perfectly glad to be proved wrong but I very much doubt that you'll be getting the best out of your lenses this way. When I used a TS microfucuser on my Canon 200L I found I could get far lower FWHM figures than I could by handling the focus ring directly. While I perfer to have as few electronic bits as possible, personally, I agree with Gina that fine focus is remarkably critical.

I would have thought that the tolerance or intolerance of a system with regard to focus would depend on the pixel size and the F ratio. Big pixels will stay 'sub pixel' in error for longer than small ones and steep light cones have shallower depths of field. No?

Olly

Quite right Olly. Short focal lengths and low focal ratios need very precise focussing.

[Gina]

Here is a screenshot of a partial SketchUp model showing the plates I plan to use to move the lenses for adjusting the framing. At the same time they provide the extra spacing required to attain infinity focus. These will take the lens adapters which have M42 Pentax/Praktica threads for lens mounting. (Adapters not shown nor the holes they fit into.)

[Gina]

The ali plates have just arrived in the post - great next day delivery service from InspiredSteel via ebay - http://www.ebay.co.u...984.m1439.l2649 So I hope to sort out the mounting arrangement a bit later today when I have the time.

[Gina]

Duplicate post...

[Gina]

Here's a photo showing the plates laid on the lens mounting plate with the adapters laid on top in their approximate positions. The centre plate will be fixed and just provide the necessary padding for infinity focus. The others will have about a milimetre movement centred on the reference points which should provide exact framing. The plates will have holes the right size to fit the adapters (I hope!) and I plan to use countersunk screws and nuts to fix the adapters to plates (or possibly make clearance holes in the main plate) the new plates are not thick enough for tapped holes.

[Gina]

Done some work on the plates. 10-12mm holes to miss the pillars that hold the camera mounting plate and, for the moving plates, 6mm holes to allow the plate to move with respect to the adapter fixing screws. Slight change of plan here - I decided to retain the fixing method for the adapter rings of screwing to the 5mm thick plate with threaded holes. "Penny washers" allow for movement of the adapter rings w.r.t. the screws.

As can be seen, I have still to cut the big holes where the adapter rings fit. Job for tomorrow

[shirva]

Hi Gina...how's the vibration when focussing the lenses. ..will you set up all the focus in one go at the start of capture or can you start capture on no1 then 2 ect without vibration affecting capture images.Davy