Flats - Darks - Fits - PNG - Live Stack

[tmyers]

Annotation 2020-03-08 134534.png (243.82 KiB) Viewed 2440 times

I didn't read as well as I should have. My last snip was of a SharpCap Flat captured as a single frame. Reading again I captured a single light frame. which is what is attached here. This one was at a gain of 102 and exposure of 1600 ms

[tmyers]

Dave,

In response you your latest post, I have a UHC Filter on the camera actually on the end of the 1.25" nose piece. This is not a high quality filter, just something inexpensive that helps with my Bortle 8 skies at home. I did shoot a series of single light frames with varying exposures to get closer to the 30,000 number, and attached it above. Edit: by smallest component I am assuming this would refer to my 1.25" piece between the camera and the scope. My SW 100Ed has a 2" tube that I am not taking full advantage of yet. i am assuming that would help with the vignetting

As a side question, if I change the output file in the right hand window to .fits, the file should be saved in .fits format, correct?

I have found that if I don't change to .fits in the SharpCap Settings I don't get a .fits file. the selection tool on the right doesn't always control the output file type.

[turfpit]

Tim

The UHC filter explains the exposure for the flats (does anything help with Bortle 8?). Without filters I use around 250ms. Of course the light sources could be much different in intensity. Live by the histogram - that way you get repeatable actions.

You would need to experiment with the order of optical parts. Aim for an order with the least vignetting.

if I change the output file in the right hand window to .fits, the file should be saved in .fits format, correct

Yes.

I have found that if I don't change to .fits in the SharpCap Settings I don't get a .fits file. the selection tool on the right doesn't always control the output file type

I have had that - when the exposure is short I have had the file type switch to SER. I think it is to do with Auto - I turn it off. You can set the defaults in File > Settings. I always check this before committing to a capture sequence.

I think you have enough now to make some progress.

Dave

[tmyers]

Perhaps the UHC Filter is just wishful thinking, I will try some more with out the filter.

So if I can get the flats in the range that has been suggested, should I gather a series of flats using the sharpcap Flat's tool or just gather a series of individual frames?

I have been gathering 30 flats to go along with 30 darks. Doesn't seem to matter what I do the stretched photo is worse when flats are applied than with out.

To try to prevent adding any more confusion to the scenario, I have not touched the camera or focus since imaging on the 29th. Following is a stretched image prior to applying flats. I used the color picker tool and brush in Gimp to smudge out the obvious speck you can see in the Flat

M-42 smaller.jpg (83.56 KiB) Viewed 2425 times

[turfpit]

Tim

Perhaps the UHC Filter is just wishful thinking, I will try some more with out the filter

Worth trying, also do a forum search for IDAS as q few people having good results using IDAS LPS filters.

should I gather a series of flats using the sharpcap Flat's tool or just gather a series of individual frames

That depends:

• If you are doing Live Stack then creating the master flat (and dark) in SharpCap makes sense.

• For post processing data then individual flat frames would be better.

• No harm in covering both options, the time penalty minimal given the exposure lengths.

30 of each is enough for testing the techniques.

stretched photo is worse when flats are applied than with out

You would need to upload a sample of frames to some internet facility like Dropbox in order to investigate.
[Edit: say 5 of each frame, ideally in FITS format, plus the camera settings]

Are you capturing bias frames? How was the image captured/processed?

Dave

[tmyers]

I have not been capturing bias frames. The image i forwarded is with no flats , no darks, and no bias frames.

I can forward via DropBox, but my images have been coming our as .png, even if I turn Auto off and select .fits, as discussed earlier.

I did use Gimp to stretch the resulting stacked image. Let me double check to see if any of my frames saved as Fits, and I will get back with you.

I suspect I am using what my eyes see more than utilizing the Histogram to determine gain and exposure, so what I am getting is most likely pure luck.

Getting great information here to de-mystify the process, although i will never be on your's and Robin's level with this. Regardless, I am still having fun!!!

[turfpit]

Tim

Don't worry about the bias frames for now. Also if your camera is cooled then the dark frames are less of an issue.

We need to get to the bottom of the PNG thing. A lot of information can be gleaned from a FITS frame with tools like FITS Liberator, PNG is just a picture. This can be sorted in the house with just the camera connected to the capture machine and taking some dark frames of maybe 10s duration.

Use of the histogram is key, however filters do change things.

i will never be on your's and Robin's level with this

Not true - persistence is the key and you have started well. For encouragement, have a look at my M42 journey and the dates
viewtopic.php?f=16&t=596, plus my Astrobin https://www.astrobin.com/users/turfpit/ collection.

Dave

[BlackWikkett]

If Tim is using live stacking and saving from the live stack save menu the following will generate PNG files;
"Save with Adjustments"
"Save exactly as seen"

The following will save a stacked FITS file
"Save as 16 Bit Stack"
"Save as Raw 32 Bit Stack"

-Chris

[tmyers]

I have not been doing live stacking

[BlackWikkett]

Very confused since the title of your post is "Flats - Darks - Fits - PNG - Live Stack"