First attempt at prime focus - Sun in white light

[Adam Y]

This one fought me all the way, but I'm reasonably pleased.  I naively thought I could just pop my DSLR with a t-ring and nosepiece in the diagonal and be able to get something.  Ran out of focus all the way in, and so I learned about back-focus.  Got myself the proper T-adapter along with the .63 SCT reducer/corrector and now I was able to get focus.

 

Solar cap filter > Celestron 8SE > reducer/corrector > adapters > camera.

 

Camera is just a Nikon D90 with no filters or mods.  ISO 400 with an exposure time of 1/50th of a second got me a pretty nice histogram somewhere around 80-90% in live view.  LOTS of spots on dear old Sun!!  Took about 60 frames with 20 darks and 25 flats.   Used PIPP to calibrate and sort the RAW pics according to quality and convert to .tif.  AS3 to stack, pretty much just the basic option here, keeping the best 95% of a really good set of frames.  Registax 6 for wavelets then over to GIMP for some mild stretching exercises.  I used Colour > Levels to align the RGB channels, then boosted up the red just a touch until it was pleasing enough to my eye without being garish.  That part is subjective, I know. 

 

Now I really want to get a Lunt or Coronado!  But for now I'll get back on track with DSO stuff as soon as it is warm enough that I feel like standing around outside all night.  Might try the moon while I'm at it!  Thanks for looking, this is fun.

 

[TerryMcK]

Nice shot Adam. Try a touch of edge sharpening to show the surface granularity a bit more.

I use a refractor with a Hershel wedge for white light and also have a dedicated Daystar sun scope, again another refractor, with its own Ha Quark.

Note you might not be able to use a Quark nor a Hershel wedge on your reflector as the telescope objective is not normally covered with a cap - the wedge or Quark doing the energy reduction.

With the solar cap on the front of the OTA it might not let enough light through to be able to capture the shorter exposure videos necessary for solar work. If you remove the solar cap, or energy reduction filter, from the front of a reflector then the temperatures generated within the OTA can cause things to melt. Not good 😞

You don’t see any overheating within uncovered small refractors of up to 4 to 5” aperture.

 

I normally take 4 to 8ms exposures in a short video of about 1000 frames. Don’t worry about flats nor darks on solar stuff as they are not really necessary. If you really wanted to do flats then just set the scope out of focus and shoot a few more frames.

[Adam Y]

Thanks Terry,

 

Would the GIMP sharpening tool work for edge sharpening?  I did try a little of that but started to see sensor patterns or something so I backed off.

 

let me know what you think might work within the set of tools I have.  I would love to bring out the granularity more, I can tell it’s in there!

[TerryMcK]

2 hours ago, Adam Y said:

Would the GIMP sharpening tool work for edge sharpening

Absolutely. Try it in very small increments. Try not to over do it though and do it before colouring.