Guiding equipment advice please

[Ewan]

Morning everyone,

I would like to buy the best / correct equip to start guiding, as in my sig i have a C8 SCT on a cg-5 gt mount, 10 x 60 Altair finder, DMK 21618 & toucam pro ii (no long exposure mod).

Am i correct in thinking i can either buy a dedicated guide cam with st-4 port & use my altair finder & off i go? But would the finder be suitable for good guiding ?, it is an F3.75 & Fl of 225mm doublet & i would use my toucam pro 2 or DMK be better, this would mean i need this as well HitecAstro Usb guider ? Does this plug in the mount or handset ? Is it as good (probably not & slower to send commands)?, or do i get an 80mm guidescope & proper guidecam ? or dedicated guide cam + finder.

The hitec usb guider is £59 but would be better spent going towards a dedicated guidecam.

Lot of questions but very new to guiding & want to get it correct.

Thanks for any advice.

[swag72]

The general feeling is that finderscopes can guide fine up to a maximum focal length of about 900mm. I used mine at 900mm and I don't think it was the guiding that was my problem!

So I use an Altair Astro 10x60 finder guider and a QHY5 camera. This has an ST4 port and so with an ST4 cable you can connect from the camera to the mount (guider port) and using PHD (and of course the right drivers!!) you should be on your way.

If you don't use ST4, you can always guide via EQMOD, but I'm not sure if you can use any camera for that - I'm sure someone will be along soon to clarify.

Another good scope for guiding is the ST80 - Many people use these.

[chrisshillito]

Whether you use a guide cam with integrated st-4 port or use an external box to provide the st-4 signals really doesn't matter. In the first case the guider application has to capture/process an image and send the correction instruction back to the camera, in the second case it sends it to the guide box instead - so no real difference.

If the celestron ascom driver for your mount supports pulse guiding then you could forget ST-4 all together and have the guider application send corrections direct to the mount/hand controller's serial interface.

Chris.

P.S. All of EQMOD is a red herring as it doesn't support your mount.

[Rwetherell]

Ewan,

I had some difficulty in getting my webcam setup with Hitecastro USB guider working for the simple reason i had only three USB ports on my laptop and as I am using my Canon 40d through Nebulosity it meant having that I would have to have 2 of my camera's attached to the computer through a powered USB hub which wasn't a possibility for me.

I decided to go down the route of a dedicated guider and bought a QHY5 second hand from someone on this site. After some difficulty getting it set up I'm now up and running.

If you've got 4 USB ports on your computer you might be okay. Otherwise you might want to look at a dedicated guider. If you decide to go down the Hitecastro route PM me.

Richard

[opticalpath]

A guide camera with its own ST4 interface keeps life simple - no additional interface boxes required.

You will want to set guide camera exposures roughly in the range 1-4 seconds so your ToUcam wouldn't do unless you LX mod it - and then you have interface and control cable requirements to sort out. The DMK would work but again needs the USB interface box.

Will you be imaging with the C8? At 2000 mm focal length you would really be testing the mount tracking and auto-guide setup. Any flexure or weakness at all in the guide system (or mirror flop in the C8) will be a source of constant frustration, believe me! Your finder would not be suitable at this image scale. Even with your 0.63x F.R. and a focal length of say 1260 mm, I'd say it would be marginal. As others have said, a ST80 makes a good guide scope; if you go for one, get everything locked down tight to eliminate any slop in the drawtube and camera mounting.

However, having imaged with an SCT myself and tried both guiding methods, my preferred option at 1260mm F.L. is an OAG. It just removes at a stroke the frustrating guiding problems caused by differential flexure and mirror flop.

Adrian

[Ewan]

Thanks for all the advice so far.

The general feeling is that finderscopes can guide fine up to a maximum focal length of about 900mm. I used mine at 900mm and I don't think it was the guiding that was my problem!

So I use an Altair Astro 10x60 finder guider and a QHY5 camera. This has an ST4 port and so with an ST4 cable you can connect from the camera to the mount (guider port) and using PHD (and of course the right drivers!!) you should be on your way.

If you don't use ST4, you can always guide via EQMOD, but I'm not sure if you can use any camera for that - I'm sure someone will be along soon to clarify.

Another good scope for guiding is the ST80 - Many people use these.

When you refer to FL of 900mm i presume you do mean the main scope's FL ?, so am i being totally stupid & expecting way too much from my kit ?

Would i actually be wasting my time trying to do DSO's & guiding using a C8 as i keep getting conflicting advice tbh, i thought, regardless of scope FL to a point, that the guiding is more precise than the mount's automatic tracking computer ?, i appreciate there are a lot of targets too big for my scopes fov but there are a lot of targets that do fit even more so using the 6.3FR.

I get pretty good tracking with the built in tracking but was looking forward to doing a few minutes at least, maybe i would be better off just keeping the SCT for planetary, lunar & solar & buying a frac after all then & then get guinding sorted ?

I just seem to keep going in circles & not getting a definitive yes or no, i really do appreciate the advice from all of you though & i guess more homework is in order.

[swag72]

Yes I was referring to the focal length of the main scope. I can not speak for whether your current scope is up to it, but if you are serious in imaging DSO's then there's a good reason why many imagers have an ED80 (or something similar) and an HEQ5 - It is probably the most plug and play scope / mount that you'll get. I've never tried to image planets, so I really cannot help on that score.

If you are wasting many nights with inaccurate guiding, or other problems, then for me, with your fickle weather in the UK, you're not gaining anything. Far better to get the right tools for the job from the off and then the nights wasted are at least taking you in the right direction. I take it that you have the book 'Making Every Photon Count'? It's regarded very highly by DSO imagers, again for a good reason.

I'm sure that someone will come along soon and say that with your kit, DSO AP is doable. But for me, I like to keep it as simple as I can. AP is hard enough at times without fighting with kit night after night that may perform OK with a few tweaks or may not. I like knowing that I go and fire up my kit and it works night after night, with the odd hicup of course!!

[Freddie]

Ewan, pop your DMK on your finder (if you haven't got an adaptor, ~£20) and get the hitec/shoestring USB (£60) and PHD (free). For £80 you have all you need. Try it out and if you find the C8 FL is too long to get the sub length you are looking for and need to move to a shorter FL scope, you still have all the guiding kit you need and no money wasted.

[Tinker1947]

If you want the best a Lodestar and a OAG may be the way to go, if this would suit you present scope, i am clueless.....

[Ewan]

Cheers guys, i know it's not an easy one to decide on, my scope IS better suited to Planets,Lunar & Solar BUT there are some really good DSO shots out there using this scope, at 1280fl with the FR it is as i see it a capable performer.

I may get flamed for the next bit sorry if it seems a little daft though,

I was thinking (maybe too simplified) that as my scope is 203mm & can have a FL of 6.3 it gathers more light & quicker than say a Skywatcher Evostar 80ED @ f7.5, this is what is throwing me a little i guess, by the numbers the C* should easily be able to do what the EVO can & with shorter exposure's, so where or what am i getting wrong ?

I am looking at getting one of these two maybe this year if work goes well http://www.firstlightoptics.com/pro-series/skywatcher-evostar-80ed-ds-pro-outfit.html or http://www.firstlightoptics.com/equinox/skywatcher-equinox-80-apo-pro-ota.html

I will (for now) get the guiding adapter for the Altair & the HitecUSB & try my DMK & see what gives, it may be terrible & the results not worth posting, mount may not put up wirth it all but at least i tried for myself i guess & for the sake of £80ish, i needed all the advice above as that's what SGL is good at & i really appreciate all the input.

Once i get up & running i am sure i will be back with some results if i have any hair left.

Ewan