[pingflood]

But if I interpret the use of DSLRs in astrophotography correctly they are rarely used for really long exposures (over 30s) anyway, because the image quality improves dramatically by stacking loads of short expsoures, instead of taking long ones. And for a time frame of 30s I can even use my "old" K20 for producing stacked images.

Stacking is definitely the way to go, but the advice I've gotten from people I've recently talked to with a lot of DSLR imaging experience says that for many objects your subs need to be in the 2-5 minute range even when stacking, since many nebulas etc are so faint. The best shots I've seen of objects like the horsehead nebula have been composed from exposures in that range, with lots of subframes.

For some reason all the astro books I've looked at so far say 'buy Canon' and leave it at that -- I am guessing they mostly look at Canon and Nikon though, and probably aren't giving Pentax a fair try.

[PentaxPoke]

Here is a shot I did when I had the K-7, of the Sagittarius section of the Milky way. It used the FA35 f/2 lens at f/2.4 and ISO 3200. Nothing great, but its not too bad. It is a stack of 8 images, and if I recall correctly, 20 second exposures each.

You are right ping that 2-5 min is typical for deep sky object stacking. But it does require equitorial tracking. It is a heck of a lot better than the film days though when we would have to expose a single exposure for hours while looking through a reticle to make sure the tracking didn't drift.

I think Canon and Nikon are recommended alot because they are not only more prevalent, but there are a wide range of astrophotography accessories available; particularly for Canon. On some of the cameras on those brands you can turn off the DFS which is nice for stacking astrophotographs because it cuts your time in half. Also, Canon made a version of the 20D called the 20Da. The "a" stood for astrophotography, and it had reduced noise, and a different low pass filter in front of the sensor for better sensitivity to astronomical objects.

One thing I found odd is that the k10d and k20d seemed to be a bit better for astro because of the raw sensor noise on the k-7. The k-7 wasn't bad though.

[ytterbium]

What I'm wondering is what situation you are in that requires fast low light AF that MF cannot remedy? Also, what do you need tethering for?

That is the thing. I didn't bought a DSLR to search for various remedies. I bought it for its actual functions. Besides, my eyesight is not that good and the factory focusing screen is not suitable for effective manual focus. I tried split prism, but needed shim, i could not get, again, because the local Pentax support is near zero.

Tethering is very useful for time lapses for example. I'm also very disappointed that most third party lenses come crippled but same or more priced in Pentax mount (like no HSM for Sigma lenses, except few).
I understand the reasons, but again it's a search for an excuse instead of the chance to have up-to-date system.
What's the economical benefit for having in-body SR if every Tamron and Sigma lens with it removed costs the same or more as OS/VR equipped version for other brands?

I would not like to give up weather sealing (that is referring to the option of getting a K-x/m to partially satisfy my needs).

If i could directly switch to canon body + 28mm/f1.8 USM (or 24-105 f/4 L USM) +all the needed basic accessories, i would.

Currently my most concerns, while sticking with Pentax is what to do with some redundant parts (no one want's my other 18-55, V1, i have to sell it ridiculously cheap or what..) and theoretically i'd like to have auto flash with zoom. But maybe i should just resist the time and get along without a decent flash.

Impressive image you have there PentaxPoke. I like the natural colours. Many use to oversaturate their astro images.

[Ash]

What Canon camera and lenses would you be going for that are weather sealed? Would you pay that much for it? You may have to consider your personal cost/benefit ratio with your needs/wants list to work out what you're willing to go for.

[pingflood]

Pentaxpoke: I read that Nikon often is not recommend for AP, because of amp glow noise in so many of their models, and the inability to turn off DFS on many/most/all. But I have no personal experience with them.

That's a really nice widefield, by the way.

As for the Canon 20Da, a couple of people I chatted with who own them said that these days they'd just buy a 20D/30D/40D/50D and have it modified instead since the 20Da carries such a high price on the used market. I wonder how a modded 50D would perform...

[ytterbium]

Yeah. So, for now i'm sticking with my current Pentax, and if nothing changes until it becomes unusable i go Canon. Currently the switchover itself is not the question that should be decided.

Still cant figure if i should...
1. sell everything but basic kit?
2. sell all rarely used stuff associated with Pentax?
3. leave everything as is?
4. any of the the above and buy 360 or some of the Metz P-TTL flash?
5. do 2., 4. and try to get 35/2 as well.
Keeping in mind that in current situation if i had the need or chance (kit lens/body defect, funds), i would switch instead of keeping the Pentax system functional.

P.S. If i get non-waeather sealed Canon/Lens, i'd be using some sort of external "sealing", like camera armour or plastic bag .

[PentaxPoke]

Keeping in mind that in current situation if i had the need or chance (kit lens/body defect, funds), i would switch instead of keeping the Pentax system functional.

If this is the case, then your used equipment will never be worth more than it is right now. It continues to depreciate. I'll bet you could get $500 for the camera, DA70 ltd. and the two kit lenses. IMO, if you are going to jump, jump now while your equipment still has some value.

[johnmflores]

Yeah. So, for now i'm sticking with my current Pentax, and if nothing changes until it becomes unusable i go Canon. Currently the switchover itself is not the question that should be decided.

Still cant figure if i should...
1. sell everything but basic kit?
2. sell all rarely used stuff associated with Pentax?
3. leave everything as is?
4. any of the the above and buy 360 or some of the Metz P-TTL flash?
5. do 2., 4. and try to get 35/2 as well.
Keeping in mind that in current situation if i had the need or chance (kit lens/body defect, funds), i would switch instead of keeping the Pentax system functional.

P.S. If i get non-waeather sealed Canon/Lens, i'd be using some sort of external "sealing", like camera armour or plastic bag .

Wait, your willing to put a plastic bag around a Canon but won't buy a K-x because it's not weather sealed?

I use a K20d and just bought a K-x as a second body/camera for wife. The K-x is a revelation, beating the K20d not only in low-light, but also in focus speed and FPS. Not only that, but the magnified Live View is more accurate than and split prism and very usable for stationary or slow moving objects.

Weathersealed with a bag, it may be a good route to consider..

[B Grace]

I also have a K200D and 18-55 kit lens but I rarely use the lens. If I wanted to upgrade by switching from the Pentax to a Canon kit the minimum Canon I would consider would be the 5D whatever Mk it is right now.

[ytterbium]

I also have a K200D and 18-55 kit lens but I rarely use the lens. If I wanted to upgrade by switching from the Pentax to a Canon kit the minimum Canon I would consider would be the 5D whatever Mk it is right now.

Those cameras are too big and expensice to justify.

Weathersealed with a bag, it may be a good route to consider..

The bag was just a joke . I'd buy some real solution if i had to. Rain coat, or whatever it is called.

If K-x did not have forced DFS, no remote release socket and had LiIon, I'd considered it.

It seems that you all think that the system should be switched or current problems solved instead of thinking how to settle with current kit the best way.

[Ash]

Your current kit isn't so bad, but do appreciate that it is limited in its capabilities, especially that which you really wanted - low-light AF performance.

The K200D is fine as is - not the speediest of AF machines, but decent enough, and it should do OK with long exposure photography. Again, where the biggest gains will be for you is the lens you put on it. Otherwise, carrying around a torch, or just turning on more ambient lights may be a simpler solution in your low-light endeavours.

[rkt]

@ ytterbium ... what did you do finally?

I ask because I also wanted to step up from a K200D + some ok lenses to something higher up the ladder, but when I just tried to offload the existing gear, I am quite horrified by the demand and prices for all that I have to sell... which was all bought first hand within the last 14 months ... and I do not intend to collect about 30-40% of the initial outlay in just such short a period of time...

[ytterbium]

Yeah, the value for second hand Pentax gear is very low if you want to sell it fast. There is next to no demand. If you want to sell it for a reasonable price, you might wait of 2 to 3 months until someone finally needs the item your'e selling. And its the other way around, when buying something.

Still, ive choosen to stick with Pentax.. for now. Ive researched that to get the performance i want, i had to buy gear i'm not willing to carry around. The big 40D or better and L lenses - unnafordable and heavy.
With the af improvements in K-x and K-7 and the technological innovations in 645D i expect there are very satisfactory options when my k200d fails on me.