Guiding guru's please apply - Autoguiding help

[PH-R]

Hello all,

After spending hours and I mean hours yesterday trying to work out what I actually need for manual guiding/ auto guiding I decided to post here for hopefully some advice on the way to go.

Firstly I have got a budget of £100 (I know not a lot but that’s it) The equipment I already have Skywatcher 100ED, standard EQ6 mount, vesta webcam, canon D10, 3x Barlow and a 9mm IR.

My understanding from the threads I have read is to forget the manual guiding route.

So it looks like autoguiding is going to be the path I take. Is my understanding correct that all I need to do is to modify my hand controller which will cost about £4.00 from shoestring obtain a connection for the parallel port which I think I can get one second hand for £20 some quality guide scope rings which I have obtained from Arthur on this site £30 and use some free software like guidedog. This then leaves me £50 for a cheap scope because I have read that as long as it can focus on a star quality is not really an issue.

Will the above give me a basic autoguiding system? Also does the handcontroller mod allow lx200 commands to be sent, how does it work?

I know a lot of questions but hopefully I can get all the answers in one place and it will be useful for others.

Thank you and best wishes,

Paul

[Whippy]

I'll be honest and say that trying to do this a cheaply as possible could just be an exercise in frustration. In theory, and old scope can serve as guide scope as long you can bring the camera into focus, but it'll be better if you can find something with as short focal length as possible so you have the widest FOV as possible for picking out a guidestar. You might be able to find a ST80 for £50 but it might take a bit of looking.

Just a thought, but have you tried getting accurate polar alignment and doing some unguided images before you delve into guiding?

Tony..

[moondog]

I'd second Tony's advice to try and find an ST80. A lot of us use this scope as it's a 'fast' scope' (F5) you should be able to find decent guide stars.

MD

[PH-R]

HI Tony,

Thank you for your reply. Yes you are right astrophotography on a shoestring. However, I can always add to the kit later when the house is all finished and the good lady allows me more pocket money.

I started astrophotography last year and only managed to get out for M31 on a few nights and found that only being able to take 60s shots would take double/treble the time as the pic had to be downloaded through a usb 1 cable, so to obtain just 1hour of data would take me my whole session. So if I can increase the exposure time I think I can get more data on the limited nights I am out. ( I live in wales :-) )

I have seen two ex demo cheap meade scopes one is 90mm and the other 70mm. However, they are both F10's, which is not fast. Could I make them faster by using barlows and a diagnol?

Please see photo which is 32mins of data I think using the unguided system.

Regards,

PAul

[Whippy]

That's a nice M31 you got there .

The thing you need to think about is focal length Paul. The two scopes you mentioned are 700mm (70mm) and 900mm (90mm), in comparison the ST80 is only 400mm. Barlows make the focal length longer so you'd only make the situation worse if you used one! My only thought that might work would be is to buy a cheap x0.5 focal reducer that sits in the nosepiece of the camera. This would shorten the focal length and give you a better chance of finding a guide star. That might work, although I've never done it so a bit of googling might be in order.

I still think getting your polar alignment dead on would be a better option, I'm sure you'd be able to get longer subs like that. Have you looked at using WCS to help? I use it with my setup and it does the job. In the meantime, you could save up for the EQ6 synscan upgrade (it's got a guide port built in on the motherboard) and look at getting better kit for guiding.

WCS: Polar Alignment - WCS - Fast and accurate polaralignment for astronomical mounts, using a CCD / webcam and drift alignment .

Tony..

[steppenwolf]

I think you would be better off trying really hard to get an ST80 right from the start because this instrument works very well indeed in this role and although you may well expand/upgrade your other imaging gear, this 'scope will keep you in good stead in the future. This scope is sold under the Skywatcher, Orion, Celestron and Konus brand names. Its 400mm focal length gives a good field of viewfrom which to choose your guide star and its F5 aperture will help collect suficient light from fainter stars.

Using a webcam does work although unless it is modified (more expense!) you will be limited in your choice of stars because of the short exposure lengths it will allow you.

Modifying the hand controller is what I originally did, this is simple to do, a bit 'clunky' as it means guiding at 1 X Sidereal rate but again, it certainly does work quite well.

You mention LX200 commands and, in fact, that is how I originally controlled my mount but that was only because at the time, the only interface that I could find details on was one that acted as an LX200 'emulator'. I built this emulator from a kit of parts and it worked flawlessly but there are cheaper options available using now using simple opto-isolators and a good source for these is 'Shoestring Astronomy'.

A quick look at my website and this page in particular will give you more information on this.

[PH-R]

Hello Steve and Tony,

Thank you very much for the advice so far.

Steve, great info on your site and that is exactly what I will be doing. I have just ordered the 'Guide port Conversion Kit for EQ-style mounts' also it was great looking at your picture's and the progress you have made since starting astrophotography, well done the pictures are great.

Tony, what a great idea with the focal reducer I have found one for £24 which I will buy if I can get the 90mm scope cheap enough. Could you tell me how it will all fit together please. I have a mogg adaptor for the web cam, does the reducer connect to this directly and then is it inserted directly into the scope? or is there yet more kit to buy? Oh I forgot to say I will be getting the WCS software, thxs for the link.

Thank you both for your time,

Kind regards,

Paul

[Whippy]

The reducer normally has a 1.25" fitting so it should fit into a normal nosepiece, which in turn should go into the focuser of the scope.

Tony..

[PH-R]

Hello,

My lovely wife gave me the ok to buy Startravel - Skywatcher Startravel 80 OTA So thank you again for the advice.

I will post an update when all the kit is set up and working.

Paul

[PH-R]

Hello,

Right update so far, I have modified the hand controller using the instructions here: http://www.store.shoestringastronomy.com/eq_mod.pdf and made some slight modifications see my method below:

Pic one tools I used, please note I did not use the multimetre.

Pic 2 This is where I did it slightly different from the guide above. I chose insted not to remove the main board and simply used a tie to attach the new lead to the main lead.

Pic 3 I found it useful to tape the first lead to be soldered in place as my hands were full. After the first one was in place I could just solder direct without the wires dropping.

Pic 5 All done :-)

Not showing on the pictures is the last job, which was applying a small amount of silicone (external type) around the new wire for waterproofing.

All credit to Doug Anderson who wrote the guide above and figured out this wonderful simple mod.

Total time about an hour.

When the adapter GPINT-PT arrives next week I will get to test everything works fine.

Paul

[Whippy]

Congrats on the ST80, that should serve you well and fingers crossed on the handset mod. I've got a CG5 with dual drives that I normally use for observing but I'd be interested to see if it could make a handy backup if my EQ6 is otherwise engaged.

Tony..

[PH-R]

Quick update got the chance to go outside today and make sure the handcontroller still works since the mod and it.......................................................................................................................... does :-)

As soon as the adaptor arrives I will give another update.

Paul

[PH-R]

Update:

I have the guiderings (thxs again Arthur), I have the new St80 delivered today (thxs Steve) see pics below and I have converted the handcontroller. I am just waiting for the adaptor and it is ago. As soon as I have the adaptor I will test and post the results of this budget guiding experiment!

Best wishes,

Paul

[PH-R]

Update:

Adaptor arrived this morning (thxs Steve) and I have just tried it out using the

GPINTCheck software and I am pleased to say everything works.

Next update weather permitting some test pictures.

Best wishes,

Paul

[PH-R]

Hi all,

Update:

Ever since getting my new equipment I have had nothing but clouds and rain . However, all this changed on Wednesday night (29th) at 10.30pm I noticed that the sky was quite clear. I am normally in bed for work at this time but as I have been waiting so long to try out my new equipment, I decided to set the mount up and test the new guide scope using PHD. I polar aligned the mount manually and selected Dubhe for my guide star due to my limited choice, as my setup was just outside the backdoor in the yard. I must say that the results seem very encouraging and I cannot wait until tonight to do some imaging. I have attached a picture of my results along with the original PHD log file.

I have some questions:

As my peak PE is 1.74arc seconds and my guide scope is 400mm and my vesta webcam is 5.6um this gives me 2.89 asec/pix so in theory perfect round stars for a 39min exposure. However, my imaging scope is 900mm and my Canon D10's chip is 7.4um giving me 1.7 asec/pix, am I correct in thinking that the above setup will easily give me 5min exposures? or have I missed something?

Also because the guide scope is faster than the image scope will it make corrections quicker than the image scope registers them?

I am sure I have missed something obvious because my cheap secondhand setup gives my potentially excellent performence!

100ED 2 pro £340

EQ6 £320

Shoestring adaptor £23

handcontoller mod, cost my time and lead £6

Vesta webcam £0.99 good old ebay

Mogg adaptor £14

St80 £104

Canon D10 £100

Power pack for D10 £20

Shutter release £15

Guide rings £30

Laptops already owned

PHD, Free

Iris, Free

So my whole set up has cost me £973 and has a peak to peak PE with guiding of 3.06 arcseconds which costs a fraction of other setups with similar results.

Obviously this is all theory at the moment but I look forward to the imaging season.

Any suggestions observations would be very welcome.

Kind regards,

PAul

PHD_log_29Jul09.txt

[Whippy]

It certainly looks promising . I'm sure you could speculate in regard to the performance of the setup but the only real surefire way of knowing is to get it out under the stars collecting photons. If you get round stars with the exposure times you want, then great. Fingers crossed for you!

Tony..

[PH-R]

Hi Tony,

Thank you for your encouragement and feedback during this thread.

The results are in and I am very encouraged by the results.

I have identified several problems I need to overcome, so the 4hr session last night was really helpful, even though I never got any data for any of my targets.

Problem 1, My handcontroller stopped sending commands to the mount from the computer or by manually pressing the buttons. PHD seemed to be sending commands still, as the light on the handcontroller was blinking like normal. The only solution was to unplug the handcontroller from the mount replug and everything worked fine again. This happened twice in four hours but I could still do with knowing what could cause this.

Problem 2, Had to a manual polar align as WCS kept crashing, need to look into this further.

Problem 3, I need to work out away to balance the scope because with the Canon attached and the guider scope attached it was not balanced so my PE increased quite abit.

All in all it was a great night and I look forward to ironing out the few issues I have.

I have attached some pictures below:

Pictures 1 & 2 A star in the constellation Cassiopeia 6min and 10min subs ISO 400 also one stacked picture of all the subs 29mins. I can already see by doing longer exposures I collect much more data than my old 60sec sub (ISO 1600) method

Obviously no darks or processing have been applied to the pictures they are just raw.

Second target A star in the constellation Ursa Major 5min (ISO800) and 10.15min (ISO600) subs.

With all the pictures I notice in the left hand top the stars seem to be slightly elongated. What causes this? Flexure or not being 100% polar alligned?

Any help or suggestions would be most welcome.

Best wishes,

PAul

[Whippy]

Looking good Paul , the guiding looks to be working which is the main thing. The elongated stars in the top left might be where the camera isn't sitting square to the focal plane in which case you'll need to make sure it's square in the focuser or where you're using a camera with a big chip, you might need a flattener. A lot people find they need one with DSLR's.

What is more noticeable IMO, is the 'intrusions' on brighter stars. Not sure what they are but they don't look too pretty. Is the light path to the camera completely clear?

Tony..

[PH-R]

What is more noticeable IMO, is the 'intrusions' on brighter stars. Not sure what they are but they don't look too pretty. Is the light path to the camera completely clear?

Tony..

Hi Tony,

I have noticed this before and it is caused by felt spacers between the lenses. I could follow an online guide and try and fix it or put some tape at the edge of the lens. However, it does not bother me and is not an issue with the targets I have lined up. If it does bother me in the long run I will take the lens apart and fix it.

Also thxs again for your help and I look forward to entering a few pictures in the image of the month thread.

Best wishes,

PAul

[Whippy]

No worries Paul, I look forward to seeing some of your images .

Tony..

[Paxo]

Paul,

Just to confirm what Tony said about a small amount of tilt in your system. I've taken the liberty to run one of your images through CCD Inspector (see attached images), it shows an 8 degree tilt from left to right across the image which is causing your slightly elongated stars. There is, however, only limited curvature onto the chip so the likelihood is that you won't require a flattener.

Images are looking good though, keep at it and you will improve on an already good start.

Steve..

[PH-R]

HI Steve,

Thank you for the very informative information, this will definitely help me.

Do you know of a free program to measure the FWHM of a star?

Also when using the ST80 I cannot achieve focus, I need to use the diagonal but I am still slightly out of focus, that surely must not help the guiding program? The only way I could achieve proper focus was using the diagonal plus 2x barlow.

Any suggestions?

Best wishes,

Paul

[minimalist]

Paul, congrats on getting your guiding sorted. Just found this thread myself. As to reaching focus with the st80 and webcam, the best answer would be a 1.25" extension tube. To calculate the length, measure how much the diagonal adds to the light path and then add how much more you need to move camera to achieve focus. Usually 25-50mm is sufficient.

Daniel

[PH-R]

Paul, congrats on getting your guiding sorted. Just found this thread myself. As to reaching focus with the st80 and webcam, the best answer would be a 1.25" extension tube. To calculate the length, measure how much the diagonal adds to the light path and then add how much more you need to move camera to achieve focus. Usually 25-50mm is sufficient.

Daniel

HI Daniel,

Thank you for the advice I will look into that option.

Kind regards,

Paul

[PH-R]

HI Steve,

Thank you for the PM reply, please see attached new image taken on the 8-8-09 with a full moon and the target low in the sky. However, must not grumble at least I had some clear skies to practice with. The image is 5mins and my setup is 1.7 asec/pix.

I made sure all the equipment was pushed into place nice and firm, so hopefully I have eliminated the 8 degree curve in the previous pictures.

Also I have attached the fruits of that four hour session 35mins of data with flats, darks & bias frames applied.

As I image with a slow scope f9 is there a way without looking at thousands of pictures of other peoples work that I can work out how many hours of data I require to bring out the best of a particular subject? For example if I imaged the attached target for 20hrs with my equipment what would the end result be like?

Thank you for your time and help with this matter,

Kind regards,

Paul