Solar imaging

gordonewen

See the attached image. I got this after processing a video shot with a Lunt 152 H-alpha scope. It is a very poor image.

I can get an ok exposure as judged by the histogram but the image is very washed out and soft. To get any sort of contrast on the laptop screen I had to set gamma at 1.0 (in Firecapture, which is as low as it will go), which seems very odd.

For comparison, here is alink to the same region of the sun taken with a DMK21AU618:

http://www.flickr.com/photos/74614447@N02/9612525791/in/pool-1891767@N21

You can see there is a great difference. Can anyone advise what is happening with the 120MM and how I can get a decent image?

Regards

Gordon

jimlafferty

I am going to try this camera for the first time on saturday with a Lunt 100 using Firecapture and will let you know what I find--I can tell you that I have never had good results trying to expose via histogram only. With my PGR grasshopper 3 and DMK 41 and Firecapture I generally have the gamma set to the minimum setting (unlike with IC Capture which seems to let me use the full range of gamma more usefully). If you try to expose with the histogram going solid black from end to end you will wash out the image. I like to get the best and most contrasty looking image on the screen and use that. If I use the histogram it is usually to insure that I dont have any part of the image overexposed.

I will post here with some first light pics later saturday.

Jim

Sam@ZWO

What is the gain setting?

16 means 1X

we suggest you set the gain biger than 16

gordonewen

Sam, I was using a gain setting of 10 to maximise the histogram range. I will try higher setting at next opportunity.

Jim, I refer to the histogram just to make sure I am not clipping the high end - see other threads on gain settings.

With DMK and IC capture I generally use a gamma setting of about 5-10% of the range the camera allows. Same with Lucam Recorder. As you do, I generally get the laptop screen view to look right and video that. Look forward to seeing your results.

Regards

Gordon

gordonewen

Sam, I tried turning up the gain to 38 and it made no difference to the bland image on screen during video capture.

This morning I set up the Lunt and then used both ZWO 120MM and DMK41AU with Firecapture to examine the histogram. The histogram with the DMK has a much wider range than that of the ZWO; a range of 35 to 250 vs 100 to 240. This would explain the bland appearance of the on screen image with the ZWO camera.

However, after sharpening the images in Registax I stretched the histogram of the ZWO image and got a pretty good result. To get a similar image with the DMK requires no stretch. So it appears that the ZWO does result in good images, but I would be interested to know why the histogram is narrow relative to the DMK - anyone have any idea's?

Regards'

Gordon

jamesf

I've been struggling to avoid the "Newton's Rings" effect with my 120MM when solar imaging in Ha. A few people seem to share the same problem, but I believe it may be a "feature" of the sensor rather than a specific problem with the camera.

James

jimlafferty

Gordon--I think you are on to something there--After I read your post above I went back and stretched the ZWO image some (like you, I never had to do much of that with the DMK 41) and the results were surprising--a lot more detail tahn appeared to be present before. I posted the image on my thread abt my ZWO test shots--

Jim

skywatcher

hello,

when i make my first sun picture in white light , i have the same problem with my ASI 120 mm

now, i make flat on the sun, and my pictures are clean

the asi 120mm is a Cmos sensor, the dmk is a CCD sensor, and the Cmos technologie don't like sun imaging, while the glass over the sensor make reflection !

keithcobby

How did you take a flat solar image? De focused image or something else?

Keith

skywatcher wrote:
hello,

when i make my first sun picture in white light , i have the same problem with my ASI 120 mm

now, i make flat on the sun, and my pictures are clean

the asi 120mm is a Cmos sensor, the dmk is a CCD sensor, and the Cmos technologie don't like sun imaging, while the glass over the sensor make reflection !

astromike

I put clingfilm over the lens and capture about 100 frames. This video is then used to generate a flat in Registax (works better for proms) or AutoStakkert (very good for batch processing disc detail.

LexAstro

Hi all, I have what will likely seem like a silly or amateur questions. I have a 4" refractor, and ZWO ASI585MC and 174MM cameras (all controlled via ASIAIR). When I try to image the sun with either camera (with a spectrum white light filter attached to the front of the telescope), I can't seem to get properly exposed images, when using 'photo' mode, vs 'video' mode. In 'photo' mode, either the images look severely over exposed, or they turn a strange purplish colour. I've turned off the 'auto' setting in the histogram, but then what I see on screen looks worse. I'm not well versed on how to interpret the ASIAIR histogram, and I assume that's part of the problem. I also don't quite understand if what I see on screen (iPad) is what's actually being recorded when the histogram is set to Auto, vs Manual, vs Zoomed in. I hope my questions make sense and appreciate any guidance and/or reference to online material I can use to better understand how all that works.

When I image Nebulae or Galaxies, I don't have any issues. It's only when I try to image the sun (very new to that). The reason I want to 'image' vs 'video' the sun, is to practice taking images for the upcoming eclipse October 14th. And, because the ASIAIR limits video to 1080P, which severely reduces the field of view 🙁

Thank you...

w7ay

LexAstro When I try to image the sun with either camera (with a spectrum white light filter attached to the front of the telescope), I can't seem to get properly exposed images

With white light filters, the Neutral Density filter is your friend:

https://www.baader-planetarium.com/en/baader-neutral-density-filter-(nd-1.8-t1.5).html

Baader has 4 of them, but you can adapt other ND filters used by photographers, too (to get long exposures of lakes and fountains to appear as mirrors :-).

You should be able to easily figure out how much ND you need to get a 32 millisecond exposure.

Chen

johnpd

By "Photo" mode do you mean you are using "Preview" mode? If yes, you cannot get the proper exposure for solar images in that mode. The exposure selections are very limited. Video mode does have a sliding exposure scale which allows you more leeway. You also mentioned the other issue with the ASIAIR in video mode: limited to 1080P which reduces the FOV available. You are much better off using something like SharpCap or FireCapture to capture solar images as they have more options and allows full resolution of you camera.

JohnD

LexAstro

johnpd

Hi John, yes, "Preview" mode. I use MacOS, so I'll try using FC again. There are limitations with FC on Mac, but I'll see if I can work around them. Also, I haven't seen an 'image capture mode' option in FC (seems it's for video capture only). Maybe I can take very short videos and process those into images. I'll research how fast the moon moves over the sun during eclipses to guesstimate the proper video length. Thanks very much for the feedback.

LexAstro

w7ay

Hi Chen, I have 2 of those badder ND filters already actually which I've used for viewing the moon. I didn't think about using them to image the sun. I currently have a filter drawer attached to my cameras when I image the sun, but I currently use that for a uv/ir cut filter which as I understand it, is needed for solar imaging along with the white light filter. If I use the ND filter only, is that ok?

w7ay

LexAstro If I use the ND filter only, is that ok?

Just stack the ND filters on top of your UV-IR cut filters.

Chen

LexAstro

w7ay Two filters don't fit inside the ZWO filter drawer...

w7ay

LexAstro Two filters don't fit inside the ZWO filter drawer...

I would stay away from ZWO filter drawers for daytime work. ZWO filter drawers leak light like a sieve. The light that leaks through the drawer is not attenuated by the white light filter either.

With the ZWO pancake cameras, you can add a 1.25" filter right into the camera's flange using a M42 (male)-1.25" (female) adapter -- no need to even stack.

Chen

LexAstro

w7ay Thanks. understood. I'll give that a try. Also, I just discovered ASI Studio!!! It supports all resolutions, and is so much easier/better to use for solar than ASIAIR!! I took a nice (according to my amateur standards) image with it today. Runs perfectly on MacOS too!! Able to control mount, EAF, EFW (for planetary) and camera!! Autofocusing is so much better too, on a big MBP 16" screen!! Thanks everyone for the nice guidance! And Chen, as always, thanks for sharing your knowledge 🙂

Finally, when you say, "no need to even stack" what do you mean? You kinda lost me there. i.e. Use two filters in two different locations, or don't bother with using the IR/Cut filter?

w7ay

LexAstro Finally, when you say, "no need to even stack" what do you mean?

Oh, I just mean that you won't need to thread one filter into an existing one. There will still be two (or more) filters in the light path. Sorry.

Chen

w7ay

LexAstro

By the way, place the ND filter as the one closest to the camera, In case the farther out filter assembly leak some light.

Chen