Wide fields from the past week...

[AlexN]

Here are a couple I've been working on over the past week or so.. I have a stack of data of a few other fields too however with a few bugs in my imaging system I'm not happy enough with them to show them at this stage..

In any case...

Here is NGC104 and NGC55.

NGC104 Details.
130x 60sec unguided subs.

NGC55 Details.
109x60s + 45x120s unguided subs.


Canon 450D full spectrum modded
300mm f/2.8 lens
Belt modded HEQ5 Pro

I'm happy to report that after extensive testing the HEQ5 seems to absolutely perfect, I went through hell with it when I bought it as the previous owner did not seem to care much about it, and had also had a shot at doing some tuning with apparently 0 knowledge of how it operates. After a strip, clean, bearing replacements, belt drive modification, polish of the RA worm and worm wheel and a re-shim followed by very careful worm adjustment I am confident that with a more careful polar alignment this mount would manage 3 minutes or maybe even more of unguided exposures with my 300mm lens... Despite not being a long focal length, the setup is still about 6kg between the lens, custom made motorized focuser bracket and finder-guider mount etc (got the finderguider in place, just no guide camera yet) At the moment I'm limited to 2 minute subs from here at f/2.8 due to light pollution however with guiding and dark skies I intend to use this rig to dig deep for dusty wonders of the galaxy.

Still working out some bugs in the imaging train, when I removed the UV/IR block and the anti aliasing filter I inadvertently changed the backfocus spacing due to the optical thickness of those two filters.. as such the lens shows poor field correction however I've got a couple of options on the burner to fix this..

Don Goldman has offered for a moderate price to make me a Lum filter to replace the optical distance of the filters removed, thus blocking the unwanted areas of the spectrum (Deep IR and UV) and correcting my backfocus distance which will return the stars to perfection (as they were prior to me pulling the filters) The other option is to simply pull out the sensor spacing shims from within the camera, moving the sensor forward ~0.9mm which will still be .3mm shy of standard, but it would have to be far better than the 1.2mm out that I am now...

Im inclined to try the spacers first as while the cost of the filter from Don is not extrememly expensive considering its a one off, it is a lot of money that I'd prefer to be spending on a guide camera...

[codemonkey]

You've been getting the rough end of the stick a bit lately, Alex, but good to see you're producing some images even with all the difficulties.

Having seen some of your raw data that one time I was blown away that you got anything usable at all with the amount of gradients you get. You should head up this way one day, I'm not too far away and the skies are nice and dark here.

Glad to hear you got the HEQ5 sorted... I'm still struggling with the NEQ6.

[Ryderscope]

Looks like its all coming along nicely Alex.
I am watching this project with interest.
Which 300mm F2.8 lens is it that you are using?
R

[RickS]

Very promising results, Alex.

[AlexN]

It's the Tokina 300mm f/2.8 SD. Same one that J-P Metsavainio used prior to getting his canon 200/1.8L.

It's actually the 2nd copy of this lens I have owned over the years. The first I sold as I couldn't figure out how most this front heavy beast securely. So I sold it in favour of an 80mm f/6 triplet. My plans now require wide and fast so try as I might to find a 200mm f/2 with a broken aperture iris or autofocus motor that I could pick up cheap, nothing became available. So, I went for the 300/2.8. I picked this one up in absolutely Mint condition for $870. It comes with a a massive lens hood and is built like a brick..

I'll be cooling the 450D to get the most of the lens until I can justify getting back to a mono ccd. I'd essentially like to go to a kai11002m based setup alas the expense will likely dictate a kaf8300...

[glend]

Alex with the front filters removed you can still focus manually, just get a Bahtinov mask on the front of the lense and adjust for the diffraction spike pattern. I would not be inclined to pull out the sensor shims as they serve to ensure proper square alignment of the sensor to the bayonet.
That brings me to an issue I see in your images, the upper left hand side shows some tails compared to the rest of the image. Unless you have cropped these images, it would appear that you have some coma in that section of the image. This may indicate an alignment problem in the sensor, or focuser. If you rotate the camera in the focuser and take a series of shots you maybe able to see if the sector 'coma' rotates as well - just a suggestion.

[AlexN]

This is a camera lens Glen, not a telescope, so I can't rotate the camera independently from the lens. Also, none of the optical flaws here were present prior to removing the filters. In discussions with J-P Metsavainio he told me that with his qhy9 when his backfocus distance was out by 1.1mm initially he suffered terrible coma and what appeared to be astigmatism however when he fitted a 1mm thick shim to the setup the lens returned to the perfect performance it was giving with his Qhy8.

I'm still able to focus without problem with this lens, the ngc55 image gave a hfd of 1.2 prior to the imaging run. And my arduino focuser was able to maintain that fairly tightly throughout the run.

My nikkor 85/1.4D however will not focus as it has a hard infinity stop and fails to reach sharp focus indicating the backfocus distance is intact incorrect on account of the filter removal.

[Bassnut]

I dont understand the motivation of imaging NGC55 with this FOV in a 200k thumbnail.

[AlexN]

Just testing Fred.

The plan is to get the imaging train fine tuned, then get guiding sorted then start imaging fields like ngc 3576 with 10 minute subs at f2.8... Or a 2 frame mosaic of the veil... I'm going to mostly focus on Supernova remnants and extended emission nebula areas from home with clip in Ha and OIII filters then head to dark skies and chase dark molecular clouds...