Guiding and Imaging

[Hightower]

Can somebody help me, or point me to a post that has already been made that helps.

I have a few queries:

1) Should PHD guiding work well on an AZ GOTO mount?

2) Is it possible to use PHD guiding at the same time as capturing all from the same webcam?

More for curiosity and learning than anything else.

Thanks,

[johnrt]

If you are looking to autoguide for long exposure DSO imaging the an AZ mount is not suitable at all. You need an Equatorial mount. AZ mount will exhibit field rotation even in very short exposures.

You can't image and guide through the same camera, unless you have one of those fancy Starlight Express ones that support this - and I assume you don't!

[symesie04]

I agree even with guiding (and some AZ mounts do support it) this type of mount is totally useless for astrophotography. The guiding wont really give you any improvements over the internal tracking capabilities. This will be o.k for planetary work but wont suffice for DSO. You will need a suitable EQ mount for that.

Regard the camera it is possible with some fo the expensive SBIG type CCD's etc as they have a seperate small CCD that is used for guiding, but other wise no you cannot use the same camera.

[Hightower]

Thanks for prompt responses. Not upgrading my scope/mount for a while so will knock the whole idea on the head

[jgs001]

there's no need to knock it on the head, as it never hurts to practice and using a simple AltAz is a great way to learn... you just have to find, understand and work within it's limits. Now, you can image with up to about 2 minute subs (if the drives can hack it, and my SLT were not really up to the job, losing 50% of subs) low in the east and west, dropping to around 30-40seconds N/S and overhead. What can you do with that... using my unmodded SLR, I was able to capture the bubble nebula (infrared) with a huge stack of subs. For example...

Now, not so sure on using a webcam, it would have to be modded for long exposures... I'd suggest using a lightweight short focal length and just try it and see. As has been said, guiding is not worth trying to setup at this stage.

I'm assuming you have one of the lighter weight AltAz mounts, not one with a built in wedge of anything like that, you don't mention the exact setup you have in mind.

[Spikey]

I've just had a look at your photos Hightower and they are actually pretty good considering the equipment you are using so well done.

I agree with John, obviously it's not an ideal setup BUT you could use it and get some acceptable results. I'm sure you know that AP does begin with the best mount you can afford with the HEQ5 being touted as the serious entry level mount.

As John says work within the mounts limits, if you can only get 30 second subs choose a bright target and lots of exposures, M42,M45,M31 for starters...

Get a second hand DSLR and drop that into your 130p, plenty of decent ones about for the £100-200 mark.

I'm not sure if it's worth guiding or not, it can be done on an Alt/Az mount as can EQMOD but I feel it may introduce more problems than it may solve.

[jgs001]

You may need to lightly mod the 130p to work with an SLR... move the mirror up the tube a little to achieve focus... that I think can be done with the collimation bolts... (bear in mind I've never used one so can't say for certain). The other thing I'd suggest, get a pair of tube rings and at least a medium size dovetail... that way you can put the camera on top (by rotating the tube) reducing odd pull in the system from the position of the camera, and allow leeway for balancing... you don't want it perfect, you need the rear, in this case it'd be the primary mirror assembly to be "heavier" so the mount is always lifting and keeping the gears engaged. I did balance mine too well at one point and could not longer get exposures over 5 to 10 seconds...

[Hightower]

Hey folks, thanks for all the advice. I didn't mean knocking the imaging on the head, just the idea of guiding etc. I'm actually loving that I can image on a £4 webcam, and am just looking for the next progression already. I'd like to start and capture nebs and things, and think my next investment will be a SPC880 (if I can get my hands on one!).

Like the next fella, I suppose I'm just looking for the next step.

[riklaunim]

Webcams are much better for lunary and planetary imaging. Although SPC880/900NC may be hardware-modded to support long exposures needed in DS imaging - the result may be dissapointing to some

[jgs001]

It'd be worth having a look at somewhere like

Used Canon | Secondhand Canon | Used Canon DSLR | Second Hand Canon

They have SLR's from £120... I know that's a lot more money than an SPC880/900... but it won't need modding for long exposures.

[Hightower]

Thanks for the link. That's always an option and something that I might look into. Was planning on getting a DSLR for our honeymoon. Will I need a lens (correct term?) as well, or only if I plan to use it as a normal camera?

[jgs001]

You only need a lens if you're planning on using an SLR as a normal camera. If for AP only, then the telescope is the lens.

[Hightower]

You only need a lens if you're planning on using an SLR as a normal camera. If for AP only, then the telescope is the lens.

Ok, last one (for now!). If I went with the cheapest available, the 350d, what else would I need to connect this to the telescope and also have computer controlled shutter (guessing thats the easiest way).

[symesie04]

jgs001 have to say thats a really nice image. Quite impressed with that.

Hightower yes i think i jumped the gun a little there and have to appologise. When i think of DSO images a automatically think of tight in nebula's and galaxies etc, this im afraid the mount really wont be up to. However if you do decide to go DSLR route and piggy back it with a wide angle lens you could still do some really nice wide field photography, see jgs001's image above and many others on this forum. With a really accurately alligned AZ mount some have claimed as long as 5 min subs when doing wide field. You will need some software capable of stacking and rotating though. Good luck either way.

[Spikey]

Ok, last one (for now!). If I went with the cheapest available, the 350d, what else would I need to connect this to the telescope and also have computer controlled shutter (guessing thats the easiest way).

Watch out if you're using Windows 7, the 350D doesn't have drivers for Windows 7.

[jgs001]

jgs001 have to say thats a really nice image. Quite impressed with that.

Hightower yes i think i jumped the gun a little there and have to appologise. When i think of DSO images a automatically think of tight in nebula's and galaxies etc, this im afraid the mount really wont be up to. However if you do decide to go DSLR route and piggy back it with a wide angle lens you could still do some really nice wide field photography, see jgs001's image above and many others on this forum. With a really accurately alligned AZ mount some have claimed as long as 5 min subs when doing wide field. You will need some software capable of stacking and rotating though. Good luck either way.

Thanks...

I really don't think in AltAz mode, that 5 minutes is doable... everything I read (and I read a lot) indicated that the maximum is 2 minutes or field rotation sets in. That image was with a SW ST80, so pretty light and short. My SLT mount really struggled with my 80ED, it's a much heavier and longer beast.

As for computer control, that's not really necessary... you can just get a cheap timer remote from ebay (about £30 to £40) and let that control the camera, works great. You'll want a focus mask for the 350d though.

For between image derotation, the stacking process in DSS will take care of that for you, that image I posted was over several nights and DSS just put them all together.

[Hightower]

What about this one: Canon EOS 300 / EOS Rebel 2000 135 mm Camera: Amazon.co.uk: Electronics

Could this be a start for me?

[symesie04]

High tower i thinks that a film dslr and not digital. Although still useable for astrophotography it will makes things incredibly more dificult. I would therefore advise you advoid. Digital will have a D designation after the model, i.e 300d 350d etc.

jgs001

yes but the st80 is still 400mm focal length i believe. I was refering to something like a 20mm or less fast lens for wide field.

[Hightower]

High tower i thinks that a film dslr and not digital. Although still useable for astrophotography it will makes things incredibly more dificult. I would therefore advise you advoid. Digital will have a D designation after the model, i.e 300d 350d etc.

I'd suspected as much, but couldn't quite fathom. 350d it looks like then.

[jgs001]

yes but the st80 is still 400mm focal length i believe. I was refering to something like a 20mm or less fast lens for wide field.

Ah, gotcha... everything I read, indicated that the maximum exposure length in AltAz is not affected by the focal length of the tube.. of course, a longer focal length is going to show up any drive errors for more than a really short focal length, thus a really short focal length is going to help. I think, the ST80 and 450d combo weighed between 1 and 1.5 Kg (I can't remember now)...

Hightower, if you can spend a bit more and get a 400d then the issues with amp glow is resolved... the 350d suffers from it in long exposures, whereas I believe the 400d does not. Even then, you can use darks to remove the amp glow, so it's not a big headache.

[Hightower]

Ok, you've sold me. I'll be making the upgrade to the 400D. Any more advice before I take the plunge?

[jgs001]

Sort yourself a bhatinov mask too, help you to focus with, you can either make your own, or buy one from flo

[symesie04]

A 500d would give you live view which can really help in focusing lol

[Hightower]

A 500d would give you live view which can really help in focusing lol

Lol, 400d really is my limit as a start in DSLR's

As for Bahtinov, it was one of the first things I made (laser cutter at work) and it works a treat with my webcam.

[jgs001]

Oh... depending on how your connecting the camera, something like the SW LPR filter is a good idea.. it'll have 2 effects... 1) May help with LP, and 2) keeps extra dust out of the camera body.