[phatbob02]

But....

You are in a thread about long exposure astrophotos. What is missing from the Kx that my older K100Ds and filterless K110D have and everyone wants is an electrical cable release. We want a computer or handheld controller to time dozens of exposures of minutes each.

I once came within an hour or so of ordering a Kx. What stopped me is when I read on this forum that it lacked the electrical connector for a cable release, the connector for external power, and the ability to take long exposures without Noise Reduction (AKA Dark Frame). All these items are on a K100D.

I feel Pentax does not care about us astrophotographers.

Leo,
I just posted the release bracket to help the NewBees.
I purchases the Kx for the sensor, not requiring mods, and because of the price of just over $500. I can live with not turning off NR over 30". And, the Kx external power supply is available. Pentax K-AC84U AC Adapter Kit.
There are people out there getting great results with this camera.

Astronomy Forums | Telescope Forums & Reviews | Astronomy Community - Kx for astro imaging

I'm "old School" when it comes to AP. I use to hyper my own film. I own a SBig St-237 and ST-8i.
Not everyone has $4500 to shell out for an ST4000XCM, and I think you're comparing apples to oranges.

For NewBee's, this is a great camera to start with. If you're thinking of getting into AP, I would recommend a good motor driven mount.

You can still enjoy the hobby without spending a wad of cash. Not all of us need software to turn on this and turn off that. The learning curve and cost of imaging processing software will keep you busy enough in the beginning.

[orly_andico]

1) on the K20D it's possible (via debug mode) to disable the dark frame subtraction; however this trick doesn't work on the K-x; not so horrible, use ISO 12800 and stack and stack and stack..

2) K-x can be controlled via the PK Tether software through the USB cable

That said, I'd snap up an 8300C if I had the moolah.. dedicated astro-camera is really much more convenient than a DSLR (currently suffering with a DSI.. although I plan to relegate it to guide camera and use my new-old 40D as my astro-camera).

[LeoTaylor]

Hi phatbob02

I'll go down your list line by line.

> I just posted the release bracket to help the NewBees.

As I started out my message, I think you did a fine job. But since I take typically several dozen 3 minute frames per night I don't want to hold my finger on a mechanical shutter release. Besides, it's cold out there!


> I purchases the Kx for the sensor, not requiring mods, and because of the price of just over $500.

Fine again. I purchased my K110D new for $349 for astrophotography only. I only used it four days before I opened it up and removed the IR filter. I broke it in the process, had Pentax fix it for $210, still had an astro DSLR for less than the cost of a professionally modified Canon. I used it for several years. It currently has 10,600+ shutter clicks, almost all astro. I don't want you to think I don't like DSLR astrophotography.

> I can live with not turning off NR over 30".

OK, but many can't as you can tell from the number of complaints that has been brought up since the K20D came out. At first many assumed it was an oversight and Pentax would fix that in a firmware upgrade. I think all Pentax cameras with CMOS sensors don't allow NR to be totally disabled like the K1x0Ds.


> And, the Kx external power supply is available. Pentax K-AC84U AC Adapter Kit.

I wrote there was a kludgey method that uses the same power supply as the K100D. For less than a nickle they could have put a jack on the outside.


> There are people out there getting great results with this camera.

No doubt, the Initial Poster likes it very much.

> I'm "old School" when it comes to AP. I use to hyper my own film.

You're brave. I used a K1000 for several years with refrigerated film. My wife would not let me hyper, "too dangerous to have compressed gas in the house." She was a lab technician and has seen gas cylinders fly across rooms and through walls.

> I own a SBig St-237 and ST-8i.

You have seen the promised land.

> Not everyone has $4500 to shell out for an ST4000XCM, and I think you're comparing apples to oranges.

Absolutely, though I only paid $3750 from OPT. I had reached my limit with the K110D. I was spoiled by the DSLR one-shot-color but wanted to go back to a cooled camera since my ST-7E cut through my light pollution far better than film or DSLR. I can easily capture image MAG 19 galaxies from my MAG 3 sky. I sold the old SBIG to help pay for the new SBIG..

Nothing in my observatory cost me over $900 (the price of my used SCT) except the SBIG. I normally do photography on the cheap, but there was no way around buying an SBIG for me to move forward from the DSLR.


> For NewBee's, this is a great camera to start with.

Perhaps. As I wrote I almost bought one for the features it has over my K110D. Unfortunately it took away features as well.

> If you're thinking of getting into AP, I would recommend a good motor driven mount.

I use my LX200 Classic as a motor drive for a refractor, camera lens, and my 2080 OTA. One motor for all worlds. On those occasions I go remote for darker sky I use a CG-4 with RA. motor.

> Not all of us need software to turn on this and turn off that.

I'm not sure what you mean by the on and off part. I do use software (or a timer box in the field) to operate the shutter. I also use software to point the scope at a target. With the DSLR that was about it. With the SBIG all camera operation must be with software, it can't function on its own.
----------------

My point is you can do astrophotography with a Pentax DSLR, I did for several years (and over 10,600 shutter clicks). I used my K100DS for the lunar eclipse because SBIGs don't do solar system imaging well. I'm just frustrated that Pentax seems to go out of their way to thwart astrophotography. They remove jacks that cost practically nothing. It troubles me when after years of them ignoring requests for a menu option to disable NR someone tricks a camera into factory debug mode and finds such that option exists hidden inside.

I love my Pentax cameras for daytime photos. I can even use my astro modified filterless K110D as a killer IR camera. I measured 100 times faster IR response than my K100Ds

[orly_andico]

after exercising the trick no-DFS mode on the K20D more extensively, I have this to report..

it's noisy!! there's a huge amount of noise that dark frames cannot eliminate (so it must be thermal noise). my stacks are riddled with black dots from where Deep Sky Stacker subtracted "hot" pixels from my master dark.

[ursamajor]

Which is better for astrophoto: K-x or K-r? This is my dilema.

[ursamajor]

Please, can anyone do a comparison between two models, from the astrophotography's point of view?
I'll buy soon my first Pentax and I'm not decided, yet.
Thanks!

[oliver939]

I'm new here but I saw Andy's astrophotos on faceBook and I was sold on the K-x.
I know one of the draw backs with the cam was the lack of a cable release, so I made a bracket and thought I'd share it.

It's 1/8" PVC sheet stock from my local hobby and a hotshoe adapter from eBay.
Total cost is $13 with the cable release and it works great.

I haven't had a chance to try the camera yet. I live in Syracuse, NY and we've had 76" of snow just for December.

this is a piece of "bravoure" but dont the Kx as a jack socket for remote shutter?
I do a bit of astrophoto with a K100DS using a single cable with a jack plug. It is very easy, light on the camera and cheap (even super easy do diy).

Another thing, everybody discusses about the Kx (and Kr) here but what about the new K5?
After a K100DS, I think it worthes to go the step above with K5 (it also has DFS disabling option) but I can not find astrophotographer feedback about it.

thanks

[angus]

I have the K-5 after doing some astroshots with K10D and astrotrac before. The difference is amazing. Unfortunately my attachment budget is pretty much used up, but I managed to shoot the plejades from a light-polluted balcony using my 300/2.8 lens and ISO 12800, 25600 and 51200 and got away without guiding with already some of the haze showing (in the stacked pic) - I can't wait to get out into darker areas with my astrotrac.

Here's a straight JPEG ooc at 12800 with 1/2 sec and nothing done to it.

Angus


I've since removed the pic due to download limits

[oliver939]

not bad at all for a jpg.
With using some raw, few treatments, and staking several pics, you could get soem very nice details.

nb: what is this 300/2.8 lens? the one I see on the market is the DA* 300 F4.

[outpostbob]

Angus wrote:
some feedback on K-5
I have the K-5 after doing some astroshots with K10D and astrotrac before. The difference is amazing. Unfortunately my attachment budget is pretty much used up, but I managed to shoot the plejades from a light-polluted balcony using my 300/2.8 lens and ISO 12800, 25600 and 51200 and got away without guiding with already some of the haze showing (in the stacked pic) - I can't wait to get out into darker areas with my astrotrac.

Here's a straight JPEG ooc at 12800 with 1/2 sec and nothing done to it.

Angus



Thanks for that post... Here are my requests:

1. You should be able to get away with about 2.5 seconds of exposure at 300mm without trailing (i.e. fixed tripod, not using the AstroTrac.) Can you show us what that exposure duration would give you at the different ISO's?

2. What I REALLY want to see is the same series done on The Orion Nebula (M-42,) to see how the red sensitivity is on the K-5! The red sensitivity of the stock Kx is WAY better than anything else I have seen. (All the Canons must have the UV/IR filter on the sensor replaced with one that has decent pass at 653 nm, whereas the Kx is very good stock.)

I have done a similar fixed tripod exercise with the Kx, using a William Optics 90mm ED refractor telecompressed to 300mm, shooting at ISO 12,800. After stacking about 60 such images (IIRC) using Deepsky Stacker, you get a surprisingly good image of the Nebula, including the outer loop.

I would happily settle for single images, because I am DYING to know if the K5 red sensitivity is anything like the Kx.

Thanks!
Bob

[Ex Finn.]

I am DYING to know if the K5 red sensitivity is anything like the Kx.

If the K5 is anything like the rest of Pentax flagships, the IR filter is very strong compared to the lesser models.
Your astro images are very nice BTW.

[angus]

not bad at all for a jpg.
With using some raw, few treatments, and staking several pics, you could get soem very nice details.

nb: what is this 300/2.8 lens? the one I see on the market is the DA* 300 F4.

True, I have done some stacking and in the result you can see the nebula around some of the stars - it is a Sigma 300/2.8 by the way.

Angus

[angus]

some feedback on K-5

1. You should be able to get away with about 2.5 seconds of exposure at 300mm without trailing (i.e. fixed tripod, not using the AstroTrac.) Can you show us what that exposure duration would give you at the different ISO's? [

Unfortunately the longest is less than a second - you're basically shooting with an angle of view like a 450mm lens...
2. What I REALLY want to see is the same series done on The Orion Nebula (M-42,) to see how the red sensitivity is on the K-5! The red sensitivity of the stock Kx is WAY better than anything else I have seen. (All the Canons must have the UV/IR filter on the sensor replaced with one that has decent pass at 653 nm, whereas the Kx is very good stock.)

I have done so, though in a mid-town environment with lots of light pollution, however, a trip with some astro friends is planned for next weekend, a darker part of Krautland and I will show some results if we get clear skies - enclosed find an appetiser - one straight JPEG and the result of stacked JPEGs taken @ 12800 and 25600 ISO in fitswork

I downsized these considerably because of the limited download capacity and will remove at least the bigger one later

Angus

Edit: replaced pics with one stack from 26 exposures plus a single exposure which was just too long @ 2 secs

[outpostbob]

Thanks, Angus! I am encouraged, since the stacked image does indeed show a fair amount of red. Were ALL the exposures 0.3 seconds as you data showed? How many such subframes did you stack?

My 2.5 second exposure suggestion was based on a rule from Michael Covington's "Astrophotography for the Amateur." The original rule as published (for 35mm frames) was Max Exposure = 1200mm-sec, so a 300mm lens would allow 4 seconds to meet "no obvious trailing of stars" parameter. (More is possible if you are far from the celestial equator but that is irrelevant for Orion.) For APS-size frames, this would be reduced by the lens factor, so you want to keep the exposure below 800mm-sec. 2.5 sec x 300mm = 750mm-sec, so you should be OK. Now, since you were in a light polluted area, with a fast (f/2.8) lens, I can imagine that there was simply too much light to avoid washing out the entire frame with longer exposures than you used, especially at highest ISO. (Brad Miller and I use ISO 12,800 pretty much exclusively in our Kx's. But around home I MUST use light pollution rejection filters...)

I will look forward to seeing what you get from a dark location! Let us see what the most extreme frames look like, if you would. $1500 is a big enough purchase for me that I want to be VERY sure I will like the outcome.... and you're our only hope, Obiwan Kenobi! <G>

Bob

[jbinpg]

One of the first night shots I took with my K-5. This is of Taurus with the FA 50/1.4 at f2.0, 8s, ISO6400. There is considerable coma toward the edges of the frame which would have improved with stopping down. Noise reduction and exposure adjustment done in RawTherapee. Pretty impressive. My K20 would not have had a hope of replicating this.