Eyepeice Projection + Webcam + DSO's?

[Roy Batty]

Hi,

I've got a SC1.5 modded webcam and was wondering if anyone could advise me if eyepiece projection imaging as opposed to prime focus would be more suitable for DSO's using a webcam?

So far my efforts at trying to obtain even an image i can preview and check focus with have been in vain e.g. M13, M57, M27 are these bright enough to show an image in preview?. although i don't seem to have any trouble getting a view from stars e.g. Alberio?

Hence my question about eyepiece projection - would this present a brighter image onto the ccd?

Also is it essential to have an IR / UV filter to get an image?

RB

[Ant]

Hi Roy,

With a webcam, you want the largest possible fov. Which is prime focus, EP projection is what I used to image planets and the FOV is very small indeed!

When I first hooked up the SC1 to my 6" Newt on M13, I was getting the DSO showing after as little as 5 seconds (might even have been slightly less than that).

How long were the exposure times? Are you sure that the webcan was focused? If your getting a star in the FOV (stupid question - but was it a star or hot pixel, that's fooled me before) then the focus should be OK. Maybe you just need to turn the gain up.

I used to turn the gain right up - to locate the object with the lowest possible exposure and then after centering adjust accordingly.

So

1) Make sure that the focus is good

2) Make sure that the object isn't dissapering off the chip suring the fine focusing - with the standard R&P focuser that I had it was an issue.

3) Turn the gain right up.

4) If the SC1 mod is the switch version - make sure the switch is in the correct position.

5) Ensure that you have the second lead attached (parrellel one).

Hope this helps, it's sort of a list of the things that I've done wrong in the past and things I've done to put it right.

Ant

[Roy Batty]

Hi Roy,

With a webcam, you want the largest possible fov. Which is prime focus, EP projection is what I used to image planets and the FOV is very small indeed!

When I first hooked up the SC1 to my 6" Newt on M13, I was getting the DSO showing after as little as 5 seconds (might even have been slightly less than that).

How long were the exposure times? Are you sure that the webcan was focused? If your getting a star in the FOV (stupid question - but was it a star or hot pixel, that's fooled me before) then the focus should be OK. Maybe you just need to turn the gain up.

I used to turn the gain right up - to locate the object with the lowest possible exposure and then after centering adjust accordingly.

So

1) Make sure that the focus is good

2) Make sure that the object isn't dissapering off the chip suring the fine focusing - with the standard R&P focuser that I had it was an issue.

3) Turn the gain right up.

4) If the SC1 mod is the switch version - make sure the switch is in the correct position.

5) Ensure that you have the second lead attached (parrellel one).

Hope this helps, it's sort of a list of the things that I've done wrong in the past and things I've done to put it right.

Ant

Ant,

thanks- quite a list ...

I've previously had the gain set at around 80% - 90% using K3CCD when previewing, so i'll try it at 100% next time.

Is it best to preview in long exposure (lx) mode i'm using k3CCD 3 i.e. set up the preview to say: half, 1 or 2 second exposure?

The cameras lowest default preview (non lx) is: 1/25th shutter at 5 frames per second, is this not enough to get an image?

RB

[Ant]

Is it best to preview in long exposure (lx) mode i'm using k3CCD 3 i.e. set up the preview to say: half, 1 or 2 second exposure?

The cameras lowest default preview (non lx) is: 1/25th shutter at 5 frames per second, is this not enough to get an image?

RB

I would definatley preview in LX mode - 5 seconds would be my starting point. But if you then want a quicker preview (to make focusing a little quicker), you can lower the exposure - but do that slowly, i.e. go to 4 seconds make sure the object is still visible. Then 3 seconds etc etc...

Cheers

Ant

[Ant]

Sorry forgot to say...

at 1/25 sec on DSO I doubt that you will get anything at all.

Sorry to be all negative!

Ant

[Roy Batty]

Ant,

thanks for the advice

I guess i'm on a big learning curve, first steps are always somehow the hardest but most rewarding ones

RB

[Ant]

No worries Roy, I remember sitting at the laptop trying to get everything to work for the first time - I also remember the first time I saw the image of M13 appear on the screen.

It took days to remove the smile from my face

I look forward to seeing the end result!

One last tip, make a note of the setting used... If the image is pants you know what not to do again, if the image is good you can duplicate it again easily.

Ant

[Kaptain Klevtsov]

OK, so here's the drill. I'm assuming that you have a way of getting the target on the camera chip, or close enough that you can find it fairly easily.

Use the webcam at prime focus. As has already been mentioned Ep projection is not good for DSO stuff.

Using non LX mode, aim at a bright star and get the focus as good as you can. Lock the focus, check its still OK then leave it alone. The only time you should refocus on a DSO in LX mode is when you need to be in a bad mood quickly.

Slew the 'scope to the target and go into LX mode. Turn up the gain all the way and go for as long as you can manage with your patience setting. 5 seconds should have something to see on most of the brighter things like Globs and clusters.

Centre the image very slowly. If you get it off the chip, its bad. Often very bad, uless you can reaquire it.

On the K3CCD LX screen, there's a histogram setting that you can use to stretch the preview even more. This has no effect on the saved AVI so just use this for targeting.

Adjust the time so that the high number in the brightness level meter is above half way up (150 ish). That's switched on by the pile of colours under where it says processing just under the blue border at the top if its not on already.

Hit record, grab the binos and give it a few minutes. If the target is still centred on the chip, give it some more minutes.

Make sure you know where its putting the AVIs. You will probably want to find them later. Also make sure that you check advanced file naming and use incremental so as not to overwrite the file each time you do a new one. This is in options, settings, video capture.

Kaptain Klevtsov

[Roy Batty]

thanks again guys (Ant, KK) for the advice...

all we need now are some clear skies again

still at least it keeps my other half happy while i catch up on the diy list (never ending!)

RB