iTelescope files

[Tweedledee]

I have downloaded lots of image files on several objects from my account with iTelescope. For each object, I have two sets of subs with slightly different filenames which seem identical to each other. An example of the seemingly duplicated file names are as follows. They range from 001.fit to 008.fit for this particular object...

calibrated-t20-petersull-ngc663-20151207-202112-luminance-bin1-e-240-001.fit

t20-petersull-ngc663-20151207-202112-luminance-bin1-e-240-001.fit

 

Each of these files are about the same size, 20mb and the timestamp shows they were taken at exactly the same time.

Obviously one set is calibrated (whatever that means). Can someone explain what the difference is between the two sets of files and is there a reason for stacking one set or the other.

 

I'm currently at the very bottom of that learning curve with Deep Sky Stacker, and don't really have a clue, to the point where after watching youtube tutorials and reading the online manual, the stacking/stretching I've done so far has produced far worse looking images than just one of the much smaller 279 Kilobyte jpeg's iTelescope supplied below. I'm actually highly delighted with this jpeg, so is it actually possible to improve on this single jpeg?...

 

[Doc]

Wow so many stars. What are we looking at Pete? 

[Perkil8r]

The calibrated ones will have had flats and bias applied. In other words they are corrected for errors in both the internal noise of the camera and for imperfections optically such as dust on sensors, optics and such and also for vignetting. You might be able to see very subtle differences between then if you look closely. IMO I would just use the calibrated ones. The uncallibrated ones will be raw as it were so all imperfections will be there.

 

Stacking will help build greater detail especially in nebulae so it is well worth doing. It is not an easy thing to get the hang of but once you do you can get some really good results, pulling detail out of bits that look quite featureless before hand.

[Tweedledee]

24 minutes ago, Doc said:

Wow so many stars. What are we looking at Pete? 

Clusters in Cassiopiea over about a 4 degree wide field. The image is centred on NGC663. I think the image also contains IC166, NGC654 and 659, Czernik 4, 5, 6 and 7, Trumpler 1,  Berkeley 6 and 7, and a small portion of M103.

28 minutes ago, Perkil8r said:

The calibrated ones will have had flats and bias applied. In other words they are corrected for errors in both the internal noise of the camera and for imperfections optically such as dust on sensors, optics and such and also for vignetting. You might be able to see very subtle differences between then if you look closely. IMO I would just use the calibrated ones. The uncallibrated ones will be raw as it were so all imperfections will be there.

 

Stacking will help build greater detail especially in nebulae so it is well worth doing. It is not an easy thing to get the hang of but once you do you can get some really good results, pulling detail out of bits that look quite featureless before hand.

Thanks very much Mike.

 

Seeing that there is little or no nebulosity in this area, just stars, would I be wasting my time stacking and stretching.

 

Is the jpeg above about as good as it is going to get?

[Tweedledee]

If you are trying to visualise the image next to a star map, it is in a correct orientation and a north arrow pointing to the NCP would point horizontally to the right.

[Perkil8r]

If there isn't any nebulosity there is likely not much point in doing much more IMO as the image is good and clean. If it were full of nebulosity it would be much more worth while. That's not to say there wouldn't be any improvement in the above image but it would be less noticeable than with say the Veil or something.

[Tweedledee]

Cheers Mike, that is what I was hoping you'd say, and it pleases me no end.

 

This means that when I image clusters (not associated with nebulosity) similar to the above, I can get away with just one 4 minute sub and no stacking or processing. Thus saving time and making the most of my iTelescope points.

 

I will be having a go at stacking when I image a nebula.

[Tweedledee]

Here are a few recent single sub jpegs I took using iTelescope.

 

I'm really pleased with these for single short subs with no processing. It is so easy to do with iTelescope.

 

This is a single 4 minute sub of Stock 2 in a wide 4 degree field, completely cut-off at the left edge of this picture is the double cluster, I intend to do another to show it side by side the double cluster. I Love to see this cluster visually, it stands out in binoculars as a large hazy patch with a sprinkling of faint stars in a good sky, and is great to explore with the extra light grasp of my ST120 at 24x in a 4.2 degree field...

 

This is a single 5 minute sub of M1 in one shot colour in about a 1 degree field...

 

 

This is a single 4 minute sub of Trumpler 3 right in the centre of a 4 degree field. Trumpler 3 is also known as Collinder 36. If you search Cr 36 in Stellarium 14 it completely misplaces it in Aries (where there is nothing), but it correctly places Trumpler 3 AKA Cr36 in Cassiopiea. Other names for this are Harvard 1, OCL 366 and Lund 101...

 

 

This is one 5 minute sub of NGC 2281 in Auriga, about 1 degree field. Obviously the tracking was amiss on this one and to me it looks like the effects of a bit of dew forming. This is a great cluster to see visually which has a small trapezium of four equal brightness stars forming a lozenge shape in the middle. That lozenge shape is much more striking in the eyepiece...