Autoguiding...

Hi,
I'm planning to go down the autoguiding route and would like some suggestions/advice from experienced persons here. My plan of action as it currently stands is this:
I have a Meade 8" LX90 on a wedge in my observatory. I have ordered a 4" f/10 mak which I should have by early to mid January. This will come in handy for the Turkey trip and I plan to use it for autoguiding afterwards.
I intend in getting the APM909 adapter for my scope which will allow it to accept the standard ST4 comands for autoguiding.
I also intend getting a losmandy plate and rings to securely mount my mak to the main scope.
In terms of autoguiding cameras, I only have an lpi and a toucam pro unmodified.

The questions I have are:
1) Am I going about this the correct way?
2) I have heard that the lpi is of very limited use for autoguiding. Is this true?
3) Is a modified webcam of any use for autoguiding?
4) How many frames a second would one need to be capturing in order to get accurate autoguiding? 1? 2? 5? more?
5) What magnitude of star would I need to be targeting in order to get a good selection of stars across the sky which are near DSOs? Mag 7? Mag 8? deeper?
6) Using the answers to 4) & 5), what camera can accomplish these? ie. what camera can output x frames per second and capture stars of magnitude x in these images on a 4" mak?
I'd greatly appreciate any advice anyone here may have.
Thanks & Clear Skies,

Hi Michael,

(This could be long)

As you might have read in some other posts I have been autoguiding for some time. First I'll lay out what I use and why I use these, I'll list all the components needed and hopefully answer your questions by doing so.

My Autoguiding setup;

Is a modified webcam, a shoestringastronomy parallel port relay box, an old P233 laptop, and guidedog v1.0.6 (which is free)

Webcam: Mine is modified but you can autoguide with a non-modified webcam too. The modified webcam allows you to autoguide on fainter stars (realistically down to about mag 10-11) you will find such a star in almost any eyepiece field. I've never had to autoguide on anything fainter than mag 8 or so as I always find a nice suitable star close to any target I choose. The problem with the non-modified webcam is you are restricted to much brighter stars brighter than mag 3 or so) these are harder to come by. Also because the non modified webcam is working in video mode, i.e. 20 frames per second or so, the stars scintillation because of seeing becomes an issue as the software tries to guide on these scintillations when it really doesnt need to. If you want to consider modding your webcam, talk to me, as I've modded several webcams at this stage and know a few of the pitfalls you might encounter.

Software: I use guidedog v1.0.6. Its free www.barkosoftware.com , it works, and its dead simple to use. It can guide to sub arc-second precision and its fully configurable for each individual setup. Steve Barkes who writes the software is currently writing a pro version in which he says he'll include lots more cool stuff, including support for the LPI which is currently not supported. Other software like K3CCDtools does sutoguiding but as I havent used it for that I cant comment on how good it is.

Parallel Port Relay Box: The computer needs some way to talk to the ST4 input socket. I use a shoestringastronomy parallel port interface for this. www.shoestringastronomy.com There is a USB version but guidedog doesnt support this yet. Tis little box of tricks turns the parallel port outputs from the software into switched signals the ST4 port understands. The box also comes with a 5metre cable which connects to the st4 port. If your scope accepts an RS232 connection you can use that (all meade and celestron scopes have one i think). My experience is the RS232 connection doesnt produce as good a result as the ST4 connection.

Laptop: You dont need anything flashy, mine is a simple P233. If you have a parallel port your in business, I've tried lots of things to get guiding with my new USB only laptop without success. Obviously any old PC would do too.

Guidescope: I use my 5" mak for guiding your 4" one will do great as long as you get the adaptor to accept 1.25" eyepieces. The losmandy plate/rings are great. I have them and they are rock solid and also allow you to position the guidescope for centering guidestars etc. I also have a cross hair eyepiece which is very useful for centering the guidestar taking the grief out of getting the guidestar on the chip.

Once you've gotten all those ducks in a row its just a case of hooking it all up and guiding, it really is amazingly simple and takes soooo much grief and frustration out of astrophotography. You'll be thrilled with the results.

Normally you would autoguide with a frequency of 1-3 seconds or so. If you are using a long exposure capable webcam then the camera is exposing during this time. With a non-LX camera the software intercepts a frame every 1-3 seconds and uses that.

As far as a camera is concerned I'd highly recommend the modified webcam as the camera of choice. It works well, allows you to guide on pretty much any star you like and is cheap. If you dont wanna modify one yourself you can buy them pre modified from atik instruments. www.atik-instruments.com all you need is that basic model like the atik-1c.

Told ya this would be long. Hope this helps.

Hi Michael,

The main issue regardless of which guiding solution you use is the periodic error in RA of the LX90. You may want to see how others are getting on with the LX90 and autoguiding, there must be a yahoo goup or somthing similar.

Assuming the LX90 is capable (and I have no idea) of giving reasonable results when driven in a autoguided config then you should be OK.

As Dave G says, probably the cheapest route would be the moded web cam route. I use a SBIG ST4, which is no longer in production but the ST5, which was the replacement is still available if somewhat expensive. The ST4 type of autoguiding is great because you don't need a PC to autoguide and it is very reliable.

If you are going to go to the expense of this type of route you may want to consider a Lumicon Cassgrian easy guider. It has a very big reducing lense that does not give the serious vignetting of the lens you currently use. Again it is not cheap!

On the image capture and processing you may want to consider one of the following;

ImagesPlus (I use this and it is great)
MaximDL (verious versions)
K3CCD
DSLRFocus

Lastly you probably want to seriously consider the IR filter mod to the 300d, otherwise you are paying alot of money for a limited return.

I am going to be looking out for a nice cheap 300d or 350d in the new year to modify for astro use only.

Any other questions? Keep them comming

Later,

Jed.

Dave,
Many thanks for taking the time to write such an informative post.

(This could be long)

No worries. Long posts usually mean detailed information and that's exactly what I'm looking for right now.

Webcam: Mine is modified but you can autoguide with a non-modified webcam too. The modified webcam allows you to autoguide on fainter stars (realistically down to about mag 10-11) you will find such a star in almost any eyepiece field. I've never had to autoguide on anything fainter than mag 8 or so as I always find a nice suitable star close to any target I choose. The problem with the non-modified webcam is you are restricted to much brighter stars brighter than mag 3 or so) these are harder to come by. Also because the non modified webcam is working in video mode, i.e. 20 frames per second or so, the stars scintillation because of seeing becomes an issue as the software tries to guide on these scintillations when it really doesnt need to. If you want to consider modding your webcam, talk to me, as I've modded several webcams at this stage and know a few of the pitfalls you might encounter.

I'll have a chat with you Dave about this if you don't mind. I do happen to have a spare toucam pro so I might consider moding this. However, I've never used a soldering iron in my life and wouldn't know a resistor from a capacitor so might need a bit of practice on something less delicate first.

Software: I use guidedog v1.0.6. Its free www.barkosoftware.com , it works, and its dead simple to use. It can guide to sub arc-second precision and its fully configurable for each individual setup. Steve Barkes who writes the software is currently writing a pro version in which he says he'll include lots more cool stuff, including support for the LPI which is currently not supported. Other software like K3CCDtools does sutoguiding but as I havent used it for that I cant comment on how good it is.

Yea, I heard of this program alright. I'll download it shortly and take a look.

Parallel Port Relay Box: The computer needs some way to talk to the ST4 input socket. I use a shoestringastronomy parallel port interface for this. www.shoestringastronomy.com There is a USB version but guidedog doesnt support this yet. Tis little box of tricks turns the parallel port outputs from the software into switched signals the ST4 port understands. The box also comes with a 5metre cable which connects to the st4 port. If your scope accepts an RS232 connection you can use that (all meade and celestron scopes have one i think). My experience is the RS232 connection doesnt produce as good a result as the ST4 connection.

I heard this about the RS232 alright so I ordered a USB version of the relay box from shoestring in the last couple of days. The average parallel to usb adapter as I understand might not work with the parallel port relay box - or at least that's my guess anyway. I looked into this issue recently when I was buying a long exposure cable for my dslr. I eventually got a usb to serial adapter & a long exposure serial cable and it works fine. I see from the link there that support for the usb cable is coming shorty, although in fairness to you, you came up with a novel way of getting around the issue. Hopefully the software will be ready shortly.

Laptop

I invested in a laptop a few months ago so this ain't a problem no more, thankfully!

Guidescope: I use my 5" mak for guiding your 4" one will do great as long as you get the adaptor to accept 1.25" eyepieces. The losmandy plate/rings are great. I have them and they are rock solid and also allow you to position the guidescope for centering guidestars etc. I also have a cross hair eyepiece which is very useful for centering the guidestar taking the grief out of getting the guidestar on the chip.

With my order for the mak, I also ordered an adaptor to take 1.25" accessories. As for the losmandy plate n rings, everyone seems to recommend them so I'll invest in them in the coming months. Mind me asking where you got your losmandy stuff from?

Once you've gotten all those ducks in a row its just a case of hooking it all up and guiding, it really is amazingly simple and takes soooo much grief and frustration out of astrophotography. You'll be thrilled with the results.

I hope you're right!

Normally you would autoguide with a frequency of 1-3 seconds or so. If you are using a long exposure capable webcam then the camera is exposing during this time. With a non-LX camera the software intercepts a frame every 1-3 seconds and uses that.

Ah, I understand how the software works now! I might try the lpi first with a 3sec exposure and I'll see what it can do. If that fails, I'll get my webcam modded.

As far as a camera is concerned I'd highly recommend the modified webcam as the camera of choice. It works well, allows you to guide on pretty much any star you like and is cheap. If you dont wanna modify one yourself you can buy them pre modified from atik instruments. www.atik-instruments.com all you need is that basic model like the atik-1c.

280yoyos for the atik-1c ain't cheap so I'll buy all my other gear first and see what camera I need then. Hopefully the lpi might do. If not, I think modding the webcam would be the way to go alright. Unless someone will sell me a cheap dsi or something!

Many thanks again for the detailed response Dave! Greatly appreciated! It confirms that I'm at least on the right track and also provided some really useful practical suggestions.
Cheers,

The main issue regardless of which guiding solution you use is the periodic error in RA of the LX90. You may want to see how others are getting on with the LX90 and autoguiding, there must be a yahoo goup or somthing similar.

Yea, there is an lx90 yahoo group alright. I posted the same post there. FWIW, the lx90 can now have it's PEC programmed so this is a big improvement.

As Dave G says, probably the cheapest route would be the moded web cam route. I use a SBIG ST4, which is no longer in production but the ST5, which was the replacement is still available if somewhat expensive. The ST4 type of autoguiding is great because you don't need a PC to autoguide and it is very reliable.

Yea, the ST4 would be the dream way of going about it alright. I'll try out the lpi and see what happens. If necessary, I'll then get the webcam modded.

If you are going to go to the expense of this type of route you may want to consider a Lumicon Cassgrian easy guider. It has a very big reducing lense that does not give the serious vignetting of the lens you currently use. Again it is not cheap!

I also considered this. The giant version doesn't fit an 8" SCT due to the reduced size of the adapter at the back of the scope. I heard mixed reports of the smaller one on the 8" so shyed away from it.

Lastly you probably want to seriously consider the IR filter mod to the 300d, otherwise you are paying alot of money for a limited return.

Looked into this a couple of months ago. To be honest, I think a heart operation would be easier, so I think I'll give it a miss. However, I wouldn't rule our investing in an astro ccd camera (SBIG, Finger Lakes etc) some time in the future if I knew I got the most from my 300d.

Thanks Jed for your suggestions and comments. Certainly provides food for thought. Greatly appreciated!

I heard this about the RS232 alright so I ordered a USB version of the relay box from shoestring in the last couple of days. The average parallel to usb adapter as I understand might not work with the parallel port relay box - or at least that's my guess anyway. I looked into this issue recently when I was buying a long exposure cable for my dslr. I eventually got a usb to serial adapter & a long exposure serial cable and it works fine. I see from the link there that support for the usb cable is coming shorty, although in fairness to you, you came up with a novel way of getting around the issue. Hopefully the software will be ready shortly.

I take it that you are aware guidedog doesnt support USB guiding yet, neither does k3ccdtools (I just had a look). So it looks like a wait for the next version of guidedog. I must also plug in my parallel port pcmcia adaptor again and see if I can get that working. I had no luck last time. I can get my modded webcam to work with a standard USB - Serial adaptor and the serial - parallel adaptor from atik. Its getting the shoestring adaptor to work with the pcmcia parallel port that I'm having the problem with. This prevents me from going to a dark site as my old laptop doesnt have a battery. Maybe I should just buy a battery or two and be done with it or get a 12v convertor and use a car battery