DSLR Woes

[peonic]

OK, I've probably (read: almost definitely) done something REALLY stupid here, but.....

Got a T-ring and adapter for my Canon 300D. Connected T-Ring to camera, and then to the adapter. Got Saturn centred in an 20mm eyepiece, swapped in the camera and tooks some shots.

Nada, nothing, black screen. Swapped back to eyepiece, Saturn still there. Decided maybe the weight of the camera was moving the mount (it's a borrowed Celestron Powerseeker 114 on a somewhat wobbly EQ mount) so I tried just using the finderscope, with the camera attached (which will normally leave the target object pretty close to the centre of the eyepiece, if not exact) again, nothing.

I'm using DSLRFocus, so tried upping the recommended ISO200/4" focussing exposure to ISO1600/30" - again nothing - just a few hot pixels. I scratch my head - light pollution here is pretty bad, and if I expose for that long with a normal lens attached, I always pick up skyglow - this has nothing, just noise. To prove this, I put the end-cap on the scope, expose another ISO1600/30" and get pretty much an identical image.

I move away from Saturn and randomly pick patches of sky that give me a good chunk of stars in the 20mm eyepiece - and again, I'm getting absolutely nothing. I try a variety of different exposure times, speeds and locations. Each time I've got stuff in the centre of the 20mm ep - and each time I get nothing but noise on the images.

I've done something REALLY stupid, haven't I?

Cheers,

Peonic

[Kaptain Klevtsov]

The DSLR will be miles out of focus compared to an eyepiece, unless you deliberately modify one so that it is parfocal with your DSLR.

What you need to do is aim at a bright star, the brightest one you can find (or a planet, or better still the moon) to get the DSLR focused.

Start with pointing the DSLR at the moon and you will get good results with a little patience. DSOs are a beep to image this way and you really need a starting point for the focus so that you are close. Snap the moon and mark the focuser with a pencil, then you can get near enough so that DSLRFocus can help you get the last microtwiddle of the focuser bang on.

Planets with a DSLR will mostly be disappointing as the planet will only cover a small part of the sensor, so you really are better off with a webcam with the tiny CCD sensor.

At least you have all the kit that you need for DSO imaging already so you are a few steps up the ladder even now. All you did was assume that the DSLR would be in focus at the same point as the eyepiece, that's where you went wrong. Get to know where the DSLR is in focus and you will be laughing.

Definitely getting there, keep at it because you are only one clear night away from getting a DSO in the DSLR.

HTH

Captain Chaos

[peonic]

Cheers CC - I'll give it another go. Thought it might have been my focussing that was out - but was just a bit miffed to have been getting nothing at all even on 30s exposures.

I've now re-alligned my finderscope so that it's bang on when the camera is attached - will make finding stuff visually more tricky, but might help me get *something* on the cameras sensor. Just need to wait until the cloud clears off!

Peonic

[moondog]

Peonic

What scope are you using ?

With a 300D on Saturn @ 800 or 1600 ISO you should need no more than 1/4 to 1/10 sec exposure, with a reasonable sized scope. Say 100 - 125mm refractor or 150mm + reflector or SCT. Like CC I think it must be badly out of focus. (the exposure times depend on how much amplification the barlow gives).

Follow CC's advice for focussing using a star or the moon, before swinging to Saturn.

8)

MD

[mhc]

Peonic,

Can you actually see anything through your camera's viewfinder? Saturn is bright enough to see.

I tried the same the other night, using my D70 on a C8-N. I found I didn't have enough backfocus

Mark

[Kaptain Klevtsov]

Mark, I think the C8-N is at the very least extremely similar to the Skywatcher Newt. You might be able to unscrew the tube that holds a 1.25" EP and then screw the T ring on the bit thats left.

peonic, you should be able to see something through the viewfinder if the focus is close. Try refocusing the camera, you should get something at least to show up.

Captain Chaos

[peonic]

Can you actually see anything through your camera's viewfinder? Saturn is bright enough to see.

To be honest, I didn't actually think to try - I'll give that a shot next time I'm not covered in cloud.

What scope are you using ?

With a 300D on Saturn @ 800 or 1600 ISO you should need no more than 1/4 to 1/10 sec exposure, with a reasonable sized scope. Say 100 - 125mm refractor or 150mm + reflector or SCT. Like CC I think it must be badly out of focus. (the exposure times depend on how much amplification the barlow gives).

Scope is a Celestron Powerseeker 114mm Reflector.

I understand I was using overlly long exposures - but thought I'd try some longer exposures because I was a bit disturbed that the usual orange glow I pick up pointing the 300D with a 'normal' lens wasn't present (I'll see it with 10-sec plus exposures everytime - but with a 30sec thru the scope, I just saw CCD noise). As for barlows, I didn't have one connected up - wanted to just get 'something' captured first before I went for magnification. That wasn't a silly thing to do, was it?

Cheers,

Peonic

[mhc]

Mark, I think the C8-N is at the very least extremely similar to the Skywatcher Newt. You might be able to unscrew the tube that holds a 1.25" EP and then screw the T ring on the bit thats left.

CC, thanks, I spotted that and it works fine for prime focus. However, I'd hoped to use eyepiece projection to get larger images of Saturn and the moon. Seems it can't be done.

I'm just a tad vexed with myself that I didn't research that bit earlier :D That and a lack of clear skies has wiped some of the pleasure from my new toy.

[peonic]

mhc,

I could kiss you!

Just nipped out to set the scope outside to allow it to cool down, and had a go at looking thru the camera's view finder whilst aiming at Venus. Could just about make out an out-of-focus blob, which I seemingly didn't have enough travel on the focusser to be able to pull sharp.

Another quick look at the t-adapter I picked up from FLO , and I find that it's actually two pieces - with just one piece attached, and using my 3x Barlow I can get reasonably decent focus by eye, with lots of play left in the focusser so it looks like I'm getting there.

Lets just hope the clouds don't roll in, and I'll head off into the garden as soon as it gets dark and see how I get on.

Thanks for all the help guys, I'm sure I'll have more questions come tomorrow!

Peonic

[mhc]

I could kiss you!

Steady on there peonic, this is a family show

Another quick look at the t-adapter I picked up from FLO , and I find that it's actually two pieces - with just one piece attached, and using my 3x Barlow I can get reasonably decent focus by eye, with lots of play left in the focusser so it looks like I'm getting there.

Mine is also in 2 parts. I had a good head scratch today and tried a different combination during daylight. I removed the T-adaptor's 1.25 inch end-piece that fits into the focuser. I removed the scope's 1.25 focuser, leaving the 2" with the T-thread on the outside. I screwed the remaining eye-piece holding tube directly to the T-ring on the focuser, with a 10mm ep in. I was then able to use eyepiece projection.

Saturn is way too small to be any use, but I reckon I'll be in with a chance on lunar shots. For planetary eyepiece projection I'll look at buying a universal adaptor and my old Canon S45 compact. It does AVIs so I should be able to mimic the webcam processing methods (registax, etc).

I also had a go using my dSLR at prime focus on M44. Had to use a lot of trial-and-error for the focusing but think I got there in the end. Off to check the results...

Hope the clouds stayed off for you!

Mark

[mhc]

Hi Peonic.

Here's what I got using D70 at prime focus. I think it's M44, the Beehive cluster

Regards,

Mark