I believe it does handle the hot pixels, but also other mostly-repeatable thermal noise ('amp glow') from the camera as well. Astrophotographers will take and stack multiple 'light' frames - the actual image - to handle random noise, then stack multiple 'dark' frames (DFS frames basically) and subtract that to handle repeatable noise, and also use a stack of 'flats' evenly illuminated 'blank' frames that show up issues in the optical system (vignetting mostly).

Neal

If you've got an old 'karrimat' type camping mat and a roll of duck tape you can make 'custom' inserts. I did similar to Richard but with a bag from Primark - very cheap but the strap snapped - luckily when it was full of exam scripts. Fairly sure I've seen Richard's pictures on DPR(?) and nicked the idea
Neal

I've got one, and I used it a lot on my MZ5 and MZ5n, and then on a DL2, and liked it. The constant aperture is nice, and it's small and light - though the build quality isn't brilliant, but OK. Image quality was consistently good across the range, and if you read reviews they're generally positive as well.

HOWEVER, they are prone to element separation - and this eventually happened to mine It's clearly visible from both the front and back as a partial fogging. Impact on image quality doesn't seem to be serious on mine, but it's mainly confined to the edges (for now) and I imagine it would be a much bigger problem if/when it gets to the centre. I very rarely use it now (only on a manual ext. tube because it's got an aperture ring) so it hasn't deteriorated further. For this reason, I wouldn't buy one unseen, and I wouldn't pay much either.

Supposedly, the Vietnamese-made ones don't have this problem, or it's less likely... or not. I don't know (mine was made in Japan).
Neal

Just had to try that - no luck though!

Neal

! I'd completely forgotten about those.
Neal

Thanks for all the replies - I think I'll just live with the K20 for now. For one thing, I'm not sure at the moment if I'm likely to use my camera lenses much, or mainly the telescope. If it turn's out just to be the telescope I may be better off getting an old and cheap Canon which, as usual, is what everybody else uses.

Some of the cable releases I had did need to be held down, but most had locking screws or collars.

Since I'm going to have to be doing about 20 (ish) exposures of several minutes each - and then a load of dark frames, and flat frames, and maybe dark flat frames, and offset frames - holding buttons down is going to drive me bonkers

Thanks again,
Neal

After some encouraging results (link) on holiday with next to no gear I'm thinking of starting to do some astrophotography again - I have most of what I'd need but, of course, the dark frame subtraction issue on the K20d is going to be a bit of a pain, though it'll do for starters.

Now, my wife would quite like a KM (though she doesn't really know that yet) which might nicely solve the problem - if there are workable ways of using Bulb mode. I know you can't use a wired remote - and the Pentax IR remote's I've seen would need you to actually hold the button down for the duration of the exposure (which will be minutes in length). So... does anybody know if there any remotes available that are 'lockable'? (for want of a better term). As far as I can see the same issues apply to the KX.

A used K10d (or K100d) would be alternatives, but I can see them only getting used for astrophotography - which seems a bit of a waste given our usual weather

Thanks in advance,
Neal

I go a couple of times a year and my DA 12-24 came from Cathay Photo in Peninsula Plaza who I'd very happily deal with again.

At the time (2007) it was significantly cheaper than the UK - not to mention actually available. But since then the UK price has fallen (OK so it's going right back up again), the £ has fallen against the Singapore $ (was £1=SG$3, now £1=SG$2.4 ish) and the Singapore prices have gone up a bit (I was quoted SG$1145 (stock item) for a DA 50-135 last year and about SG$1750 (special order) last month). So at the moment, the UK is actually cheaper - once the price rises work through that will probably change, but you won't be saving a lot.

To rain on your parade a bit more the Singapore Pentax distributor has just changed and nobody seems to know exactly what's going on - hence the change from in stock to special order I guess.

Other places that seem to be highly rated (but I haven't been to) are:
Orient Photo - but I don't think they are a Pentax stockist post the change in distributor
MS Color
Alan Photo - but not unambiguously recommended.

There's a Singapore Pentax forum here.

I'd suggest emailing places to ask if they have/can get what you want and how much it will be. Prices are quoted without sales tax (7%) but you can get that back at the airport anyway.

Sorry not to be more positive

I've done a bit of this, and am sort-of planning to do more

10 seconds at 50mm is the longest you can realistically get away with. If you practically-minded, you might be
better off making one of these - prob. cheaper and better than a fast lens.

They come in various forms - from the basic 'two-bits-of-wood' up to
computer controlled fancy versions. Googling 'barndoor tracker' or 'scotch mount' gets you a lot of info - and
some is collected here.

Minimally all you need is a couple of bits of wood, a hinge, a bolt and nut, some way of fixing it to your tripod and something (ball head?) to attach the camera to. You can align it well enough for wide-angle photography (50mm is def. wide angle in astrophotography) by just sighting along the hinge to the pole star.

On noise reduction, the usual thing to do is turn it off (problem for K20d users) and take multiple exposures, along with a few manual 'dark' frames, and then stack the result. Applications (free) for this include Registax and Lynkeos (mac). Serious astrophotography also uses other types of frame (here for example). You then need to post process a fair bit.

For really good results, an Astrotrac is supposed to be very good - just eye-wateringly expensive.

Good luck,
Neal

I know they're highly rated here anyway, but I have to acknowledge the service from SRS. They sent me out a replacement Tamron 17-50 f/2.8 before they'd even received the (front focussing) faulty one back, despite the fact that they don't know me from Adam - doubt many places would do that.

Neal