Sunspot photos - Help

JimmyH155 · #1 13-11-2006, 10:11 AM

Having failed miserably last week to view the Mercury transit due to clouds, yesterday I made up for it by having a go at imaging the sun. Sure enough there was a lovely large spot with lots of interesting dots. I have a Meade DSI camera, and made up a solar filter on my 8" SCT which consists of two circles of film about 60mm diameter each.
I got good focus and set the Autostar software to go. In the preview, the sunspot was there looking good, BUT nearby were two black spots that I thought at first were sunspots also. I checked these out with my 90mm refractor, and no extra spots visible.
I tried covering up each filter in turn - no difference. Then I tried swivelling the camera round in the eyepiece - no difference, dots still there. I can only think these dots are "artifacts" and something to do with the camera. The camera got quite hot and perhaps it is mega noise??

The temp was 30 deg C by the way. Am I trying to do too much with a cheapo imaging camera, or is there a way to eliminate this. When I looked at the .bmp image closely, I found not only the two big black dots, but another four much fainter repetitions scattered across the photo.

I would post a picture for youses all, but I am an illiterate (oldish) computer dummy, and dont know how to post the 900 Kb .bmp file. CAN ANYONE HELP??

If anyone can give me a blow by blow instruction how to post a pic, I would be grateful!!

[1ponders] (Paul) · #2 13-11-2006, 10:18 AM

Did they rotate when you rotated the camera? Also are you using a barlow and if so did you rotate that as well.

To post your pic, the quick and dirty way is to open the bmp in Paint and save as a jpeg. It will probably look horrible, but it will be reduced enought to post here. To post the photo go to the advanced page (see "Go Advanced" button below

) and select "Manage Attachments". Browse to your jpeg image and then upload, close the attachment box, then submit the post.

Definately show the image.

iceman (Mike) · #3 13-11-2006, 10:19 AM

Hi Jimmy.

What image manipulation software do you use?

If you get "irfanview" (download it, it's free), you can "save as jpeg" and adjust the quality so that the final miage is < 150k in size.

You can then upload the image to yoru post by using the "manage attachments" button.

JimmyH155 · #4 13-11-2006, 10:46 AM

I use the software that came with the Meade camera - Autostar suite. Yes, the spots did seem to move about when I rotated camera, and also when I changed the position of the genuine spot on the screen (declination) the two false spots moved nearer or farther from the good spot. Here is attempt to post a pic

Dennis · #5 13-11-2006, 11:04 AM

These look like some specks of dust on the front of the glass cover of the ccd chip in the DSI.

Cheers

Dennis

[1ponders] (Paul) · #6 13-11-2006, 11:14 AM

Lots and lots of dust bunnies

Pop off down to your local camera shop and pick up a bulb blower and from an art shop a very very very soft sable brush. Use the blower first to try to get the worst of it off and then gently dust the chip off with the brush. If you are not confident with using the brush, I use a pure cotton qtip moistened (not dripping wet) with 50/50 isopropyl alchohol and distilled water. This I then slide across the chip with an upward rolling motion to collect and lift any dust away. Avoid dragging across the chip surface. Important not to have the qtip too wet. You don't want water under the chip cover

Also check the rest of you glass element in the imaging train. Some of those dust bunnies look to be a fair way away from the chip surface. Are you using a barlow or Focal Reducer? Their surfaces will need cleaning as well using the same technique.

JimmyH155 · #7 13-11-2006, 11:50 AM

Hey, guys, I guess you are right, so thanks for that.

Yes I was using a 3.3 field flattener, but I must admit I didn't look too closely. Will inspect tonite. The Meade DSI also has a IR filter in front of the ccd so I guess there could be lots of light paths for dust bunnies. but why would those 2 spots reproduce themselves all over the screen. must be reflections eh? You dont think its anything to do with the temperature??
I will give everything a good clean and try at the weekend.

[1ponders] (Paul) · #8 13-11-2006, 11:57 AM

I doubt it would be temperature. Increased temperature generates increased noise and noise doesn't look anything like that.

The other thing to consider it to start thinking about taking Dark frames and Flat frames. Darks to remove the noise and Flats to help remove optical aberations like vignetting and dust bunnies. A clean chip is better but it's very hard to get a perfectly clean chip.

[1ponders] (Paul) · #9 13-11-2006, 11:58 AM

Oh and yes if you are imaging a bright object like the sun it is very likely you will be getting internal reflections. The bunnies will not only be blocking light but will be scattering it as well.

iceman (Mike) · #10 13-11-2006, 12:20 PM

Wow that's a lot of dust!

Harb · #11 13-11-2006, 01:54 PM

My brand new DSI Pro II was nearly as bad straight out of the unopened box on bright objects.....
A good clean and she is now perfect

cheers

ving (David) · #12 13-11-2006, 02:37 PM

dust on the dsi?
dust on the barlow (if used)?
dust on filter?

JimmyH155 · #13 13-11-2006, 03:06 PM

Hi Ving,
I checked the solar filter for dust. Yesterday it was raining pollen or bits of flowers from trees but I blew it off. All I used was the 3.3 flattener screwed straight into back of scope, then the eyepiece holder, then the DSI - thats all, no barlow. The front plate of the scope was reasonably clean - ie can never get it super clean, mirror looked good - no lumps and bumps. The 3.3 flattener I did not examine closely, but will check tonite. I will also clean the ccd. I got some isopropyl alcohol from chemist just now. He asked me what I wanted it for and I said cleaning eyepieces - then added rather flippantly "Might try some in my coffee!" He didn't see my sense of humour so I left quickly!

[1ponders] (Paul) · #14 13-11-2006, 03:25 PM

Unless you have large lumps of mud splattered on your sunfilter or corrector they shouldn't show up. They are too far down the imaging train. Big clods on the corrector and filter should only reduce the contrast. Can you see the secondary mirror (a rather large dust bunny really) on you images? No, and it's only half as far as the corrector plate. It's the stuff from the chip to the first few inches you really have to worry about.

ving (David) · #15 13-11-2006, 04:05 PM

in your coffee? hmm... wonder what that would be like

i had a similar problem once... could it be something on the chip its self? i have a lpi and theres a piece of glass infront of the chip. the glass was clean but there was dust floating around inside the lpi so i took it apart and gave it a squiz... lo n' behold! dust on the chip!