Locating/centring the AP target without a guidescope?

[Amaranthus (Barry)]

For those poor souls like me who are 'embracing the challenge' of doing DSLR astrophotography without the benefit of either a guidescope or 'live' CCD readout (are there any? ), what have you found is the most efficient way to locate and centre your faint-fuzzy targets?

I have a GOTO scope (alt-az mount), which is reasonably efficient at getting objects within the FOV of the eyepiece/camera chip, but the only way I've been able to confirm that anything except the brightest of objects are lined up properly is to take an exposure of 30s, and then check that it shows up. If it is not centred, I 'blindly' move the telescope a little in the appropriate axis, and then take another calibration shot, and so on. A bit hit-and-miss!

Is this the way it is generally done?

I can't use the method of getting the alignment correct using my reticle eyepiece and then switching to the DSLR at prime focus, because of the need to get the camera perfectly mask-focused on a bright star prior to moving to the DSO (the reticle EP is on a different focal plane).

I've only imaged bright stuff so far, but I'm concerned that with the fainter stuff that don't even show up well on a 30s exposure (prior to image processing), I may really struggle to know that it's in my FOV. I guess starfield matching is a potential solution, but I'd value any advice from the veterans on this!

[killswitch (Edison)]

Does your mount have PAE (Pointing Accuracy Enhancement) or similar? You just point your scope to a star nearby your intended subject, do PAE on that star and then slew to your subject. Your subject should be in the FOV.

[Amaranthus (Barry)]

Yes, it does have that - good idea. It's called "precise goto" on my Celestron mount. So I'd use the PAE on the bright star I've used for focussing in my DSLR, and then do the final slew to the DSO. Great tip! I'd probably still need to do some extra shots to get it exactly centred, but that would definitely help, I reckon.

[raymo]

For final framing, set your ISO to the highest your camera has, preferably at least 6400, but higher is better, and then, unless the object is extremely faint, you should record the object with an exposure of just a few seconds; remembering, of course, to reset the ISO afterwards.
raymo

[cometcatcher (Kevin)]

Yeah what Ray said. And I rely heavily on goto these days or R.A. / DEC coordinates for comets.

Having said that, I had a hard time finding IC 4628 last night. It didn't show up on 30 sec exposures at ISO 1600 so I didn't believe the goto. It was there though, right in the middle of the field! It needed 3 minutes to barely show it up!

[Amaranthus (Barry)]

What another great idea about the temporary ISO setting! Thanks guys. My camera goes up to ISO 12800 (which I would never use for shots, but should be great for this purpose).

[lazjen (Chris)]

If you drive the camera and mount from a laptop, you can use plate solving to ensure you're in the right spot. Checkout out Astrotortilla as an example. It will work out where you're pointing and if you let it, will move the mount to the correct position and verify the move.

I also do the temporary ISO trick (from the laptop) just to see if the framing is close to what I want, as I often have to move it slightly from the plate solved position to get guide stars.