m42

[alacant]

Hi everyone

Yes, sorry. Another. Excuse: we wanted to see if our bashed around 72ed was up to the standard of the swan chocolate box we had last week. Apart from the rubbish focuser, I think it is.

Colour. Not sure. This is what Siril's photo database made of it anyway.

Thanks for looking. Any other dslr/72ed/m42 shots?

700d 72ed ISO800 siril 1.0.0 rc3 StarTools 1.8.522

[alan potts]

A beautifully detailed capture, just feel the blue is a little too over saturated.

Alan

[Cozzy]

alacant

A quick search for 'SW 72ED' in the imaging forum will bring up quite a few images of M42 and many others using the same or similar kit to yourself.

HTH's

Tim

[AstroMuni]

Lovely shot @alacant There seem to be sort of halos around the brighter stars. No idea if there is a way to get rid/reduce this.

[alacant]

1 hour ago, AstroMuni said:

way to get rid

Hi

Thanks for your post.

I don't know I'm afraid. I'm not sure what causes it. Anyone?

Cheers

[Elp]

Are you using a filter?

[alacant]

6 minutes ago, Elp said:

filter

Hi

No. It's just telescope - FF - camera.

[Elp]

If you look at the halos they're relative to the centre of the image, so it looks like it's something to do with the light path, could be due to the flattener. Do you adjust the backfocus from the rear of the flattener to the camera sensor with spacers? I ask as my 61 WO flattener has a backfocus of something like 55-70mm depending on what source image you reference, I thought the dslr would connect directly to the back of the flattener via Tring but the stars were bloated when I did this.

Edited December 15, 2021 by Elp

[powerlord]

Very nice. What's this photo database in siril u mention? Sounds interesting.

[alacant]

28 minutes ago, Elp said:

something like 55-70mm

Thanks. I think you're right about the flattener.

This is a ts-flat2 which I just measured at 132mm. The advertised distance for 400mm is 128mm. Gotta be worth a try at the latter distance.

 

[Sunshine]

Wonderful capture!

[alacant]

15 minutes ago, powerlord said:

database in siril

Hi

It's under Image Processing -> Colour Calibration -> Photometric colour calibration

HTH

[ONIKKINEN]

16 minutes ago, powerlord said:

Very nice. What's this photo database in siril u mention? Sounds interesting.

I would assume this refers to the Photometric color calibration tool in Siril. The actual photometric data comes from either NOMAD or APASS surveys i think.

[ONIKKINEN]

1 minute ago, alacant said:

Hi

It's under Image Processing -> Colour Calibration -> Photometric colour calibration

HTH

If you dont like the color calibration result, try ticking off Auto and set the catalogue limit mag to a higher value? This way more stars will be used, assuming suitable stars are found in the image. I try to look at my image and see at which magnitude (referring to stellarium) the stars are still well resolved and not that noisy and choose that. Usually with mine i end up using down to mag 16 or fainter. Sometimes there is a difference, sometimes not, but worth a shot.

[alacant]

6 minutes ago, ONIKKINEN said:

ticking off Auto and set the catalogue limit mag

As I'm hopeless at colour anyway, it's a quick way to get an idea of what maybe correct. That way, so long as you adjust only the saturation, something reasonable emerges. The method breaks down though if you have removed chunks of the spectrum.

Cheers

 

[ollypenrice]

It's not unusual for refractors to struggle with blue stars at the best of times. Also, any high haze will exacerbate the problem. However, the halos are in two forms, inner and outer, and the fact that they have hard edges argues against their arising from blue bloat. They are more likely to be from internal reflections when they have a hard edge, I'd say.

Olly

[kirkster501]

A lovely picture! Well done. Yes, as Olly says, even high-end refractors can bloat the blue channel (including the luminance). Even my TEC and FSQ do a bit.

[alacant]

On 16/12/2021 at 08:35, ollypenrice said:

internal reflections

Do you mean as in Newtonian Reflectors if e.g. you don't blacken the inside of the tube/focuser/spider?

[ollypenrice]

6 minutes ago, alacant said:

Do you mean as in Newtonian Reflectors if e.g. you don't blacken the inside of the tube/focuser/spider?

No, I was thinking more of reflections shuttling back and forth between glass surfaces in the imaging train of a refractor. So that might be flattener/filter/chip window etc. Sometimes generic flatteners as devils for this. 

Olly

[alacant]

Here we are with the TSFlat2 at 128mm and a UHC filter. Yeah, I know. I changed too many variables [1], but it looks like the halos seemr more under control.

[1] I expected the filter to introduce more -or larger- reflections.

Edited January 2, 2022 by alacant
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