Auto-guiding with the DMK

[iceman (Mike)]

Anyone tried autoguiding with the DMK?

I'm sure I've read of some people doing it on the CN forum..

I don't see any reason why it would be a good guide camera?

Thoughts?

[Dennis]

Hi Mike

This should be possible. If you have the non-AS version DMK, the longest exposure is 30 secs I think, and this is more than adequate for auto guiding.

When I use my SBIG ST7 for auto guiding, the guide star exposures range from 2 to 10 secs, although the ST7 is more sensitive (and cooled) than the DMK.

I suspect you would have to use a GPUSB from Shoestring Astronomy if your EQ6 has an ST4 type auto guider port. I have used the GPUSB with my Orion Deep Space Imager ccd and Craig Stark’s free software PHD for guiding and this combo works very well indeed.

Have a read of this pdf article to get an understanding of webcam auto guiding.

WARNING – It is a long, slippery slope and it looks like you are on it. Long exposure auto guided astro photography is obsessive, and expensive!

Cheers

Dennis

[[1ponders] (Paul)]

Hi Mike, there has been some scuttlebut over at the K3CCDTools yahoo group in the previous few weeks about using the DMK with K3. Apparently it works fine as an imaging camera through K3 so I don't see why there would be any prob using it as a guide camera.

WARNING – It is a long, slippery slope and it looks like you are on it. Long exposure auto guided astro photography is obsessive, and expensive

Ya got that right Dennis but you left one thing out......maddeningly frustrating.

[Dennis]

Originally Posted by [1ponders]

Ya got that right Dennis but you left one thing out......maddeningly frustrating.

I wanted to break Mike into the black art somewhat gently, without scaring the living daylight out of him….

Cheers

Dennis

[iceman (Mike)]

Thanks guys. I'm not actually contemplating it just yet, I don't have an ED80 yet and that's a long time away as it is.

[[1ponders] (Paul)]

See if you can find an old tasco somewhere Mike. It doesn't have to be fantastic.

[g__day (Matthew)]

Okay my views on autoguiding is expensive - its kinda right, but I've pushed my gear to the limit and it works - on a real budget.

I use a Celestron CG5 mount to carry a C9.25 + 80MM Meg - which is quite heavy. This burdens the mount to about 15 - 16kgs, right at or over its intended maximum carrying capacity for visual, let alone astrophography. In its favour its on a very sturdy permanent pier, well balanced and pretty neatly polar aligned. So the tracking is pretty good to start with for visual. If I focus on a star and come back 3 hours later its moved about 1/3 of the eyepiece out of position - so its probably less than an arc minute off the SCP. Also its all housed in an astrolab - so wind, dew and the elements are kept off my gear which must help its performance.

I simply made a 6 pin connector cable of the right length, bought a ShoeString Parallel Port adapter (wish now I went the USB version that has automatic line pull down on start-up), attached a DSI via USB to my PC and generally use PHD to autoguide.

I find PHD very simple to use and tracking seems way better than I have expected. So far I haven't done longer than 10 minute shots, but I'm planning to do a few long duration shots just to get a feel for the limits of what my platform can do. My main capture camera is a Canon 400D (with filters not removed, and no external / 3rd party cooling), so long shots are likely to be noisy.

The point is a CG5 is a really questionable platform for longer duration astrophotography, let alone when it is loaded to or past its normal visual carrying capacity. Yet the results - well I'm estactic to say the least. PHD is making few corrections and 10 - 15 minute shots look fine, at least from a tracking accuracy - true colour capture is something I'll want to verify next!

To me this is not an outrageous expense:

1. Goto mount, hand controller slaved to PC via cable I build and serial port adapter, using CDC for goto control $1,300
2. Meg - second hand $400
3. Meg mounting rings, saddle plate, screws $150
3. DSI - second hand $350
3. Shoestring adapters $95
4. Cabling, connectors, serial adapters, multi-meters, crimping tools - $90
5. PHD and CDC - free

So its cost me about $1,080 to add goto to an existing mount + OTA set-up, including the second OTA. I find this pretty awesome.

I'd love to be using a better mount and capture camera, but above an eq6 I'm looking in the $5,000 - $6,000 for a capable goto mount and you could say +/- 50% of that again if you went the S-BIG path for capture and/or autoguiding. For now all I really want is more precise goto's - and I'll start playing with T-Point to see if I can make my CG5 even more accurate than you'd otherwise expect.

That will have to wait a bit, cause right now for what I've spent I have a solid enough base to learn on.

So in my case at least is auto-guiding really all that expensive?

[gbeal]

Can't see why not Mike. I use the un-modded ToUcam, and K3, so in effect the DMK is similar. I do use the ToUcam/K3 setup with Robbers StarMate though, but given some means of getting info from the PC to the mount (StarMate in my case) it really should work.
Additionally, as has been pointed out, it has long exposure capability so even better.
You sure the guide chip is cooled Dennis, perhaps more sensitive, but mine isn't cooled as far as I know.
Gary

[seeker372011 (Narayan)]

Mike

why bother? why not use your old ToUcam? or have you flogged it?

[iceman (Mike)]

nah i've still got it, just considering options. The DMK can do long exposures and is more sensitive, which I guess gives it an edge over the ToUcam.

[[1ponders] (Paul)]

I checked last night Mike and the DMK opens fine in K3, PHD Guiding and Metaguide.

I haven't used them, just opened the camera with them. Can't see why they wouldn't work though.


You can also capture through K3 (tried that) and Virtual Dub as well, though VD is a bit titchy.

[rsbfoto]

Originally Posted by [1ponders]

I checked last night Mike and the DMK opens fine in K3, PHD Guiding ....

Hi,

You mention PHD Guding opens fine a DMK .... camera ?

Which version do you have

I have no luck, have the version 1.5 pre1 and just see a screen with a lot of black and white points but no image at all.

K3... and Metaguide yes works fine.

K3... guides very nice, whereas Metaguide needs at least 5 frames per second in order to guide properly and also you can not get dim stars.

[Astroman (Andrew Wall)]

I have successfully pulse guided with the toucam and my 8" scope. Mind you I was using the EQmod way, havent tried the autoguider yet.

[[1ponders] (Paul)]

I'm using Version 1.0 Rainer. If I get some clear skies tonight ( )I'll check to make sure it works. All I did the other night was to remove the adapter cap and pointed around the room and watched the screen intensity change from very dark to overexposed when pointed near a light.

There were however no black and white points on my screen, it looked pretty smooth.

[[1ponders] (Paul)]

Well when your right your right Rainer In the very low light areas all I got was white dots on a black background.

At least it works with K3 and metaguide.