emyliano2000

I have no clue what's going on, I even opened the filterwheel to check the red filter and it's all good

24 minutes ago, emyliano2000 said:

Light leak might have happened when red lights were taken but not when flats were taken nor when blue and green channels were taken

I have SGP set to take 10 of each throughout the night to be sure I have enough of each at the end of the night so if there was a leak when I shot the red, it should've been there when I shot the other ones too

2 minutes ago, vlaiv said:

This is wrong - shorter dark must have lower mean ADU value because both darks should have same bias / offset level and only difference should be dark current build up - longer the dark - more dark current there is - higher mean ADU value.

it does seem wrong indeed. culd it be that I shot the darks with the camera in the fridge, in complete darkness and the flat darls with camera on the scope covered, outside in the garden?

15 minutes ago, emyliano2000 said:

Could you examine blue and green flat darks to see their mean ADU value and how it compares to this value?

they are all the same, 1574 ADU

1 minute ago, vlaiv said:

And their mean ADU values?

29k for green and 28k for blue

1 minute ago, vlaiv said:

How long were your blue and green flats?

2.77 for green and 3.3 for blue

Just now, emyliano2000 said:

Light leak might have happened when red lights were taken but not when flats were taken

I tried with the lights and flats from 3 separate nights with the same result, green and blue, ok, red, not

2 minutes ago, emyliano2000 said:

flat darks were taken at same settings as flats, correct?

correct

3 minutes ago, emyliano2000 said:

Could there have been a light leak while you took red flat darks?

I took all the red, green and blue at the same time

3 minutes ago, vlaiv said:

Yes, even in single frame, there is issue with calibration:

There is arc visible in bottom left corner that is due to flats

There is same arc visible in uncalibrated sub - it is feature common to both light sub and corresponding flat:

Which means that flat is under correcting.

calibrated = light / flat and calibrated has higher value than it should have - means either light signal is stronger than it should be or master flat is "weaker" than it ought to be.

Two possible explanations:

1. Light leak - any chance of that? Light leak might have happened when red lights were taken but not when flats were taken nor when blue and green channels were taken

2. Weaker master flat usually means stronger flat darks.

Now, flat darks were taken at same settings as flats, correct?

I have found rather interesting discrepancy. It is something that I would otherwise expect but under different circumstances - so it might be important or it might not be important.

This shows that 4.24 second flat darks have higher mean adu value than 120s regular darks. Such thing should not happen, but it sometimes happens on CMOS sensors. It usually happens when one has very short exposure - like less than one second because these exposures are timed by sensor it self (to enable high fps) - longer exposures are sort of bulb mode - drivers or external electronics signals start and stop of exposure.

It also means that internal calibration of sensor is different and different bias level is used - hence stronger bias in such short exposure - one of the reasons we don't use bias subs with CMOS - they are unreliable.

Here, I believe 4.24 seconds is too long exposure to have this effect. Could there have been a light leak while you took red flat darks?

How long were your blue and green flats? Could you examine blue and green flat darks to see their mean ADU value and how it compares to this value?

If you find that both green and blue flat darks have smaller mean value - smaller even than regular 120s darks (as they should have because we have less time for dark current build up) then you should retake red flat darks to eliminate possibility of light leak there.

thank you for looking into it.

so far I tried 3 ADU values for the flats and none of them worked. I tried 1500 ADU @ 2.73sec with corresponding flat darks, I tried 25000 ADU @ 4.24sec and 30000 ADU @ 2.73sec and none of them worked. The best result that I got was from the 25000 ADU @4.24sec

5 minutes ago, vlaiv said:

You have red lights, you shot red flat field and corresponding flat darks and you are using matching darks for your red lights and you are having issues with calibration?

Could you post one of each:

1. red channel light fits

2. red channel dark fits

3. red channel flat

4. red channel flat dark

(darks don't need to be specifically for red channel of course as long as they match corresponding lights).

Here's the link

https://we.tl/t-UXgwT6An08

Yes, I'll upload one of each and put a link here 

I triex stacking them in APP, pixinsight and DSS but the red lights are not corrected properly in any of them. 

3 minutes ago, vlaiv said:

Use corresponding flat for each filter. Use flat dark with corresponding flats.

Use dark that match your  lights for each filter.

Turn off all "enhancements" and "optimizations" and you should be fine.

I did, I always do. Never had problems before with any of my other scopes. 

I tried with the blue flats but it made it worse

29 minutes ago, Laurin Dave said:

How are you calibrating your flats and lights. Are you using matched flat darks and darks with no dark optimisation ?  If not this may well be the issue ..  as suggested by @Uranium235 try using a different flat to calibrate the red.. other than dust bunnies does it remove the vignetting?  Also try flattening the flats ie flatten the red flat with the green and Blue flats etc..  again other than the dust do they produce a flat image ..  

I'll give it a try but the flats look quite different.

6 minutes ago, Uranium235 said:

How clean are your filters? Because theoretically, you can use any flat from another filter (try L) to correct the red channel (as long as all your filters were clean when you took the images) - try it

thank you for the suggestion but it looks like the filters have a few of their own dust bunnies and the circle looks different in each of the flats so I don't think it will work.

Emil

Hello guys,

I finally managed to have first light with the Altair Astro 6" RC that I bought quite a while ago from a member and I'm very happy with it but I have encountered a problem that I can't find a solution for.

I shot NGC206 with the R, G and B filters, with the corresponding flats but for some reason the flats are not fully correcting the red subs. The Green and Blue seem to be ok.

I used the telescope at native focal length, 1370mm, f9 with my recently purchased QHY163M binned 2x2 to have a pixel scale of 1.14"/px

My first thought was that the filters might be a bit too far from the sensor as I'm using 1.25" filters in a SX USB filterwheel but why are the flats correcting the blue and green and not the red?

Here is a single red filter shot uncalibrated, stretched in pixinsight and saved as png

You can see a part of the circle in the bottom left of the photo

Now, here's how the master flat looks like

And here's the calibrated red lights stack

I tried all kinds of ADU values for the flats and nothig works. A friend had the same problem with the Ha filter and he fixed it by putting the flats panels further away from the tube. I tried it too with no luck.

If you have a look at the Green

and the blue stacks, they look OK

Another friend told me it's a light leak and the Red filter might be more sensitive to it than the green and blue.

Any suggestions please? I'm really excited abot this combination and I feel down in the dumps because I can't correct the red subs .

Thanks

Emil

Optolong is launching the L-extreme 7nm dual band filter soon. Their L-enhance has been praised a lot by the OSC users so I'm thinking the L-extreme will be quite nice. 

A bit pricey though. 

https://www.astroshop.eu/broadband-filters/optolong-filters-l-extreme-2-/p,66894

Emil

1 minute ago, SamAndrew said:

Results look great  How did you get the two scopes aligned? The other constraint I have, is my setup will be remote so I can't add filters in front of the OSC without a filter wheel, although I guess it's possible. The Tri-Band filters do add the possibility to shoot narrowband with the OSC.... 🤔

The thing is, I'm using 2 mounts so aligning was not a problem but I had 2 scopes on a single mount at some point and the only way to align them without spending money on one of those side by side plates, was to use some guide rings for my small refractor but I suppose you won't be able to do that with any of your scopes so you might have to invest in one if those dual rig dovetails. 

I recently started something similar to what you are planning to do. I swapped my cameras between the telescopes to have a closer FoV and pixel scale between them and to see what comes out. 

Before the change I was using my qhy183m on the AT106 at 690mm focal lenght giving me 0.72"/px and my ASI294MC on the TS65Q at 420mm focal lenght, 2.27"/px and the following fovs.

Now I'm using the qhy183m on the TS65 at 1.18"/px and the ASI294MC on the AT106 at 1.38"/px and the following Fovs

I don't have the money to invest in a second mono camera so I thought of trying it with what I already have. 

My first test target was M13 and I'm pretty pleased with how it came out. 

I spent 2 hours/setup in 2 nearly full moon nights on it, so a total of 8 hours total integration time, 4 with the mono and 4 with the OSC. With the help of APP, I extracted the channels from the calibrated OSC subs and stacked each of the extracted channels together with the mono ones. I don't know if it's the right method of doing it but the result that I got is not that bad. 

My second test was on M16 in Ha which is quite a low target for me and also goes over London. I know it's quite a bright target but shooting over London is not that pleasant. 

On this one I shot 19x300sec with the qhy183mono and a baader 3.5nm Ha filter and 19x300sec with the ASI294MC and an Astronomik 6nm Ha filter and the same as M13, I extracted the Ha from  the calibrated subs shot with the OSC and stacked them with the mono ones. 

All in all I'm pretty pleased with what I'm getting from my "dual setup" even though one is mono and one is OSC. The only thing that I don't know how I'm gonna be doing is mix the HSO subs from the mono with the subs shot with my OSC and Altair Tri-Band. I know APP can extract the Oiii from the frames shot with an OSC and a dual narrowband too, so I think I will do the same as I did with the Ha and RGB. 

Emil

Just now, Knight of Clear Skies said:

Yes, some people have suggested it's actually the tripod that's the weakest link. We also don't know what the quality control like, perhaps some are more precisely machined than others?

Yeah, it is very much possible that some are better than others. A lot of friends told me that I probably have the best eq3 in the world 😂😂

Lucky me! 😁

I bought my eq3 to have a light portable travel setup that I could easily put in the boot of my car but when I've seen what it can do I decided to put it in the garden next to my eq6 setup. Until a few days ago I've been only using my small 420mm focal lenght refractor with an ASI294MC on it but I decided to swap cameras between the telescopes and put my qhy183m on it now and even though the pixel scale is 1.18"/px compared to 2.27"/px that I had with the ASI294MC I still get nice round stars at 5min exposure. I did replace the silly aluminium tripod with a stainless steel one for increased stability and upgraded to a losmandy saddle though. 

Emil

I absolutely love my eq3, it's giving me some great results for what is considered a very low end mount. 

Sometimes the guiding is so good, I find it hard to believe it. 

Emil

A very active galaxy that would work much better with a longer focal length but I was running out of targets on my widefield setup and I thought of giving it a go to see what comes out. 

Would love to be able to take a photo of the NGC2404, absolutely impressive HII region in the galaxy. 

I cropped the original photo to give it a closer view. 

Eq3 Pro
TS65 quadruplet f6.5 imaging telescope
ZWO ASI294MC PRO cooled at -15°C
Altair 2" TriBand filter
IDAS LPS-D2 2" filter
Qhy5 guide camera
9x50 finder-guider

Tri-Band filter: 32x600sec Gain 200 Offset 10

IDAS LPS-D2 filter: 281x300sec Gain 125 Offset 30

Total integration time 28 hours and 45minutes

Emil

With this lockdown and with the clear skies that we keep having I managed to finish another 2 targets that I've been working at for a while. 

This year I will concentrate my mono setup mostly on stars that ended their lives forming planetary nebulae or supernova remnants. 🙂

So today I come to you with the mighty Crab and the cute Abell 39 😁

In the Crab nebula you can actually see the Crab pulsar too. 😁

More info on the photos on my astrobin account. 

M1: https://www.astrobin.com/2xfpw7/B/?nc=user

Abell39: https://www.astrobin.com/c206jc/B/?nc=user

Emil

Very nicely done! I'm doing it widefield at the moment, close to finishing my desired 300x5min RGB on it. Done around 50x5min Ha during the moon period. 

Emil