Taking the plunge - 47 Tuc

[sharptrack2 (Kevin)]

Hello esteemed astrophotographers! I have finally taking the first step of the perilous and challenging road of imaging far away places in the sky.

Last night I worked up enough courage to finally put the new 90mm F5.5 refractor, I picked up from China a few weeks ago, on the mount, and attach the necessary adapters I have been slowly buying, to my unmodified Canon 450D, and connect camera to said telescope.

While seeing wasn't great, I chose a popular target, 47 Tuc, that wouldn't take a whole lot of processing to realize a suitable image for my scrapbook.

Took on a very basic workflow, 20 45 second exposures, at ISO 800 and 10 darks. Stacked and processed in DSS with default settings (mostly). A little more touch up using Cyberlink PhotoDirector (like Photoshop) and export to JPEG.

Some things I can identify right away and hope will be confirmed...

- Stars not round probably due to mount not being perfectly polar aligned. Maybe some mount instability? Maybe focus out just a wee little bit.
- Coma fringing in either the scope or the camera. Images of super bright objects with a standard Canon lens also show purple fringing
- Could improve aesthetically by cropping to just the cluster or inserting a X2 barlow and centering on the cluster

Mount is a HEQ5 Pro, 2 star aligned, sitting on grass for 2 days. Telescope is made by Aquila, more probably Synta in the end. Good build overall, solid metal casing and 10:1 focuser.

The JPEG probably won't do it justice so for those who want a look at the TIF, I've tried to share it out on Onedrive via the link below.


https://1drv.ms/i/s!AlH7c1YqjBS4g60yYJuWvDirjVcviA

Any comments welcome!

[glend (Glen)]

Congratulations Kevin..and so it begins. Looking at the image i would agree it is slightly out of focus, but the 'coma' seems to be more of a tracking error as they are all aligned in the same direction. Your small refractor does sound like an achromat, which will have substantial colour aberation, and the purple fringing is pretty normal. Do you know the focal length of the scope? You could shoot through a filter like a "Fringe Killer" but you won't be able to clean it all up. That doesn't mean you can't learn the ropes with it. A Bahtinkov focus mask is pretty easy to make yourself, there is a website that allows you to download the pattern and cutout your own. I make mine from black plastic folder covers from the newsagent, cutting out the oattern with an exacto knife - it doesn't have to be to perfect as long as it produces the diffraction spike pattern required to focus on.
There are ways to clean up star shapes in Photoshop but better to try and get accurate tracking performance at this point.

[sharptrack2 (Kevin)]

Thanks Glen,

The scope is F5.5 (90 x 500).

I wasn't expecting stellar performance for $300. Its my sandbox for the moment.

The mount is not polar aligned. The location I have to set it up is far, far from even desirable, let alone optimal. Finding a star at meridian is relatively easy, but nothing is very bright, and the ecliptic is nearly impossible due to a tree. Achernar is pretty much all I can get right now and it is quite a ways off the ecliptic. Polar scope is useless due to large structure called my house. A street light prevents me from moving far enough away to clear the roof. Way too many obstacles to contemplate any serious imaging. But practice makes for better when I do get somewhere decent.

I already have the mask printed and ready for me to start cutting out, just have to find some time.

Taking it step by step, working toward using the F10 SCT eventually. Need to get a focal reducer for it. Working on file structure, and general work flow as well. Have been a little too haphazard with my storage and have data everywhere. Retirement is looking very appealing right now so I would have time to work through the tedious stuff.

Will update as I progress, happy to share the original data with anyone who wants it.