Joined the CCD club- Some Qs if I may?

[Zakalwe]

A shiny new QHY8L OSC was delivered to me this morning, so I can now apply for entry to the CCD Club:hello2:. When do I get my robes, and are there any funny handshakes involved?:)

A couple of questions, if I may:

1. Software (can of worms opened:o): I'm currently using DSS and PS5 for stacking and post processing, and am slowly getting to grips with both. I'm currently looking at Nebulosity. Should I also consider Maxim or PixInSight. I don't really want to spend a fortune, hence thinking of Nebulosity.
   The camera comes with QHY's EZCAP, which on an initial play looks OK. Should i just use that, and use the FITS Liberator and DSS? The BIG advantage of those is that they are FREE (Zakalwe likes free:icon_salut:)
   
2. I am using a SW Field Flattener, which, I believe is designed for a DSLR). I'll achieve the correct back spacing with 2 x 17mm extension tubes (+ 20mm backspace in the CCD). This will give me 54mm in comparison to the 55mm that a DSLR has. This will be OK? Or should I change the SW Field Flattener for a different one dedicated to CCDs?
   
3. Darks. Playing with the camera this morning, although it hasn't setpoint cooling, it seems to control the temps very accurately (judging by the temp info in the capture software). So I created a bank of darks at -25. I assume that I can just reuse those over and over (maybe "freshening" them up every few months)?
   
4. BIAS. I use Al's VLB to create bias files, by holding the lappie screen to the objective of the scope. I assume the process will be similar with a CCD? How should I set the exposure time though? Using a DSLR, it was a cinch....just let the camera sort it all out.
   
5. BIAS. Never used them on the DSLR (rumour has it that the Canon DSLR has BIAS info in the darks)? Any need for them with a CCD? If needed, what process should I follow?
   

I apologise in advance for the list of question. And am really appreciative if anyone can cast some light on some of the above:icon_salut:

[Catanonia]

Welcome to the club and well done on the purchase. The tradition is for the 1st week to image wearing only socks

See some answers below.

A shiny new QHY8L OSC was delivered to me this morning, so I can now apply for entry to the CCD Club:hello2:. When do I get my robes, and are there any funny handshakes involved?:)

A couple of questions, if I may:

1. Software (can of worms opened:o): I'm currently using DSS and PS5 for stacking and post processing, and am slowly getting to grips with both. I'm currently looking at Nebulosity. Should I also consider Maxim or PixInSight. I don't really want to spend a fortune, hence thinking of Nebulosity.
   The camera comes with QHY's EZCAP, which on an initial play looks OK. Should i just use that, and use the FITS Liberator and DSS? The BIG advantage of those is that they are FREE (Zakalwe likes free:icon_salut:)
   

I would consider purchasing PixInsight or at the very least getting the free download trail and playing with it. It is hard, but there are some awesome videos on Harry Page web site. Maxim is much more expensive and I have never tried nebulosity. PI is the tool for the serious people. With PI and Photoshop you will have everything you need.

See this link for an example video http://stargazerslounge.com/imaging-discussion/140465-new-pixinsight-demonstration-video-full-rgb-processing-harry-page.html

Maxim is good but a lot more than PI. With PI and Photoshop your are ready for pretty much anything after you have stacked in DSS.

1. I am using a SW Field Flattener, which, I believe is designed for a DSLR). I'll achieve the correct back spacing with 2 x 17mm extension tubes (+ 20mm backspace in the CCD). This will give me 54mm in comparison to the 55mm that a DSLR has. This will be OK? Or should I change the SW Field Flattener for a different one dedicated to CCDs?
   

If it works for DSLR, then it should work for CCD, it is just an imager chip afterall.

1. Darks. Playing with the camera this morning, although it hasn't setpoint cooling, it seems to control the temps very accurately (judging by the temp info in the capture software). So I created a bank of darks at -25. I assume that I can just reuse those over and over (maybe "freshening" them up every few months)?
   

That is how we all do it. Redo them every 6 months or so at the same cool point or the auto point on the ccd. Try to pick the same ambient temperature to do them, ie on a cloudy night so the cooler on the QHY8 can easily reach the cool point. Ie don't take darks at midday high summer and midnight in winter. They will probably be different as the cooler in the QHY8 might struggle.

1. BIAS. I use Al's VLB to create bias files, by holding the lappie screen to the objective of the scope. I assume the process will be similar with a CCD? How should I set the exposure time though? Using a DSLR, it was a cinch....just let the camera sort it all out.
   

I assume you mean flats and not bias. There is no need for bias if you use darks and flats.

Making flats can be much harder as the CCD as it is so much more sensitive and that method would not work I guess. My experience with the QHY9 tells me that.

Using your method, you subs will be over exposed unless you go really short exposure lenghs and you will probably get shutter interaction.

The trick is lower light and longer exposures around the 3 - 5 second mark.

My solution with the QHY9 is to put a clean old white teashirt (doubled up) over the scope and point it at the laptop screen with notepad full screen and adjust distance until I get 25,000 average ACU on the chip and about 5 second subs.

Not sure totally about the QHY8, but I am guessing it will be very similar. Took me ages to work out flats on the QHY9. Depends if the QHY8 is a mechanical shutter as the QHY9

1. BIAS. Never used them on the DSLR (rumour has it that the Canon DSLR has BIAS info in the darks)? Any need for them with a CCD? If needed, what process should I follow?
   

See above

I apologise in advance for the list of question. And am really appreciative if anyone can cast some light on some of the above:icon_salut:

[Zakalwe]

Thanks for taking the time to answer Catanonia......that's all very useful. Imaging socks you say? Gotta get me some of those :-)

I'll investigate PI.....looks like that is the way to go.

Flats? Ill have a play with those. The great thing about the cooled CCD is I can do them anytime I like, I guess.

[riklaunim]

Flats must be taken for the setup used (scope, the whole setup, dust particles) - so usually after/before imaging. Darks may be taken anytime if you have set point cooling in the camera.

[Grandad]

Hi Zakulwe

Welcome to headache land.

If you havn't already done so I would get a good book such as 'The new ccd astronomy' by Ron Wadaski which has loads of useful info to get you started.

Don't rush into buying any software. As a newcomer myself ,to imaging, I am looking at all the possibilities. I have downloaded Nebulosity and after using it in demo mode for some time I have decided not to buy the licence.

What works for me at the moment is to capture with the software supplied with the camera, stack etc in DSS, load the image into Fits Liberator (which I think is still free) to give a good stretch, and finally proccess in PS7.

At some later date I will probably upgrade to PS CS5.

But its all worth it when it starts to come together

[swag72]

Hi Zakulwe

If you havn't already done so I would get a good book such as 'The new ccd astronomy' by Ron Wadaski which has loads of useful info to get you started.

Almost £94 from Amazon - What's that all about? Is this book written on gold leaf paper?!!! Is there somewhere sensibly priced for this book?

[Zakalwe]

Flats must be taken for the setup used (scope, the whole setup, dust particles) - so usually after/before imaging. Darks may be taken anytime if you have set point cooling in the camera.

Doh (slaps forehead).....right, got it now.

Hi Zakulwe

Welcome to headache land.

If you havn't already done so I would get a good book such as 'The new ccd astronomy' by Ron Wadaski which has loads of useful info to get you started.

Don't rush into buying any software. As a newcomer myself ,to imaging, I am looking at all the possibilities. I have downloaded Nebulosity and after using it in demo mode for some time I have decided not to buy the licence.

What works for me at the moment is to capture with the software supplied with the camera, stack etc in DSS, load the image into Fits Liberator (which I think is still free) to give a good stretch, and finally proccess in PS7.

At some later date I will probably upgrade to PS CS5.

But its all worth it when it starts to come together

Good advice. I have a copy of FITS Liberator, and yes, it is still free.

I have set it all up as it looks like it will be clear tonight (bit windy and gusty though). So I'll give it a go with the software that I have at present and see how I get on.

[Catanonia]

Sound advice, use the trail software and make your mind up which works best for you.

[Grandad]

I paid £40 for my copy' The new ccd astronomy' but that was some years back and I never used it until recently, but it looks you can buy a download copy from the publishers for $49.

There are plenty of cheaper book options around.

[Zakalwe]

My solution with the QHY9 is to put a clean old white teashirt (doubled up) over the scope and point it at the laptop screen with notepad full screen and adjust distance until I get 25,000 average ACU on the chip and about 5 second subs.

When you say 25000 average ACU, what does that mean? I am using EZCAP to capture the images at the moment. This gives me 4 values on each capture: STD, RMS, MAX, MIN.

Can I work out ACU from these values?

[ollypenrice]

Personally I didn't find Wodaski very useful and his layer masking technique in the edition that I saw was - sorry - awful. I would have thought that forum and individual tutorials were the way to go. RobH's website has some really well done intros to key concepts like stretching in Levels and Curves. It is a long but interesting road. I now permit myself socks, one garter and half a Y front...

Olly

[Zakalwe]

It is a long but interesting road. I now permit myself socks, one garter and half a Y front...

Olly

Front half or back? Top half or bottom. Or you a one leg only man?

Dammit Olly, we need details:D

[Catanonia]

Front half or back? Top half or bottom. Or you a one leg only man?

Dammit Olly, we need details:D

Please no, the very thought of it makes me shudder Have you seen a piccy of Olly

ACU question. Use the RMS which I think is root mean square or average.

Basically you want the light peak in the levels to be about 1/3 the way from min on a scale of 0 - 65,000

[johnrt]

Welcome to CCD club.

First rule of CCD club is - don't talk about CCD club.

Second rule of CCD club is - it's cloudy, and if it's not, whatever you wanted to image is behind a tree. If it's not behind a tree or cloudy, it's day time.

I would try the demo's out too - if you give Pixinsight a go make sure you check out Harry's videos - it's quite a learning curve without them

http://www.harrysastroshed.com/pixinsighthome.html

[Grandad]

If like me, you havn't got a lot of images to practice on, follow this link and you can download some excellent images to play with.....Misti Mountain Observatory - Astronomy Pages

[MikeWilson]

Did you manage to figure out how to take those flats, Zak?

[RobH]

Re post # 2, with regard to bias not being needed if you use darks and flats.....

This isn't correct.

You need to either bias subtract (the easiest way) or dark subtract your flats in order for them to be correctly applied. If dark subtracting, the darks must be of the same exposure length as the flats.

In practice, subtracting bias gets the job done as the exposures for flats are normally pretty short.

[Zakalwe]

Re post # 2, with regard to bias not being needed if you use darks and flats.....

This isn't correct.

You need to either bias subtract (the easiest way) or dark subtract your flats in order for them to be correctly applied. If dark subtracting, the darks must be of the same exposure length as the flats.

In practice, subtracting bias gets the job done as the exposures for flats are normally pretty short.

I still haven't fully gotten my head around the whole calibration thing yet, other than taking darks when I was using the DSLR.

Based on this, will flats give me any advantage? I guess once I get into longer exposures, and many more subs then I will need them?

Does DSS handle the bias subtract or dark subtract methods? I have now got my hands on a trial of PixInSight....but it looks like an unfamiliar monster of a program. Hopefully I'll get some time to play with it before the trail period runs out.

Did you manage to figure out how to take those flats, Zak?

Not had the time to play much more with it TBH Mike. I had a quick play with doing sky flats, but the sensitivity of the camera meant the exposures were too short. I'll probably get a chance to do a Heath Robinson with an old T-shirt at the weekend.

[MikeWilson]

I still haven't fully gotten my head around the whole calibration thing yet, other than taking darks when I was using the DSLR.

Based on this, will flats give me any advantage? I guess once I get into longer exposures, and many more subs then I will need them?

Oh yes, you >need< flats to kill the vignetting and dust doughnuts/bunnies. Try stretching your image to the extreme using the levels tool and you should see the vignetting and dust that the use of flats would reduce or eliminate.

Does DSS handle the bias subtract or dark subtract methods? I have now got my hands on a trial of PixInSight....but it looks like an unfamiliar monster of a program. Hopefully I'll get some time to play with it before the trail period runs out.

If I think I understand you right, you're wondering how DSS uses bias in the subtraction/combination algorithm when you already have darks and flats that would have inherent bias in them anyway. I don't know either! And yes, PI really is a beast of a program, not much in the way of a good UI there but the results people get from it are very impressive.

Not had the time to play much more with it TBH Mike. I had a quick play with doing sky flats, but the sensitivity of the camera meant the exposures were too short. I'll probably get a chance to do a Heath Robinson with an old T-shirt at the weekend.

Ok :-)

When you do take them, I'd be interested to know what software you used and what settings, etc. With the DSLR it's simply a case of switching to Av mode and clicking away!

Best,

Mike

[Zakalwe]

When you do take them, I'd be interested to know what software you used and what settings, etc. With the DSLR it's simply a case of switching to Av mode and clicking away!

Best,

Mike

Hi Mike,

I'm using EZCap, which is the capture program supplied with the camera. It looks fairly basic, but it seems easy to use (thankfully!) and id does the job without too many quirks.

It does have a histogram function, so I can use that to judge the exposure on the flats. I reckon I'll drag the rig out and experiment with a white cloth stretched over the aperture at twilight.