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Forum: Pentax K-1 06-20-2020, 05:52 PM  
Astrotracer consistancy with a 360 mm lens
Posted By davidwright2000
Replies: 15
Views: 974
I had it on at one time. But it's possible that I inadvertantly turned it off when fussing with re-calibration. I had noticed that, when I couldn't set the exposure in B mode, the upper lcd reads, in the shutter area, "bu". That is Pentax super-secret code for 'bulb'! So it's possible that that was much of the problelm in the middle of the shoot. But not always - you don't see the little GPS icon when the gps button is off, and I'm pretty sure it was 'mostly' on.

But that doesn't explain why those final shots of Polaris show terrible results with AT on but perfect results in M mode.
Forum: Pentax K-1 06-20-2020, 10:00 AM  
Astrotracer consistancy with a 360 mm lens
Posted By davidwright2000
Replies: 15
Views: 974
Then I switched to the K-1/360 mm lens. I was able to find M-13 nearby, and took 9, 20 second exposures. (Below, 200%). They are not terrible, but not good either. At this point I had to adjust the view, and (possibly) I touched a button, because after this the electronic compass was not available, nor was the exposure time setting in AT mode. I redid the coarse and fine calibration, which made no difference, but noted that, to get exposure time adjustment, I had to press the green button, which cconfused me because it placed a sign 'off' next to the AT icon. The upper display, in the area for shutter, read 'bu' - I couldn't find any info on that in the manual. I fussed around for a while with no success, and finally moved over to Polaris - the images I showed earlier.

It seems crazy to me that AT on messes up tracking near Polaris.(The first set of images I showed)

(I would have put all this in one post, but it wasn't clear how to add text past an image.
Forum: Pentax K-1 06-20-2020, 09:49 AM  
Astrotracer consistancy with a 360 mm lens
Posted By davidwright2000
Replies: 15
Views: 974
Just some follow-up data. but my hypothesis is that either the new firmware has a bug, or my hardware for the electronic compass is defective.

The seqquend of events last night is this: I started with the K-70/135 mm Rokinon lens. AT was already calibrated on that cam, and I just dialed in the alt and az settings for M-13; Az using the electronic compass, alt using the dial on my gear head. M-13 was in the field of view on the first image, but a little low, so I adjusted and took 9, 20 second exposures. They were all identical in terms of tracking accuracy, as shown by these 200% crops:
Forum: Pentax K-1 06-20-2020, 09:17 AM  
Astrotracer consistancy with a 360 mm lens
Posted By davidwright2000
Replies: 15
Views: 974
New results that are pretty astonishing.

I was able to take a lot of images last night. I'll show only the final result, so as not to overwhelm you with data. But everything I say; I have images to back it up.

So at the end of a frustrating evening, I took images of the region about Polaris. These images below are are 4, 30 second exposures. The sequence was: AT on, AT off (Manual mode) , AT off (Manual mode) , AT on. When AT was on, the star images are TRAILED!! When it is off, the stars are perfect (since they don't move much in 30 seconds). One additional note: I recently updated to firmware 1.52, to get the electronic compass. It worked then, and it works no, but last night, it didn't!
Forum: Pentax K-1 06-19-2020, 08:46 PM  
Astrotracer consistancy with a 360 mm lens
Posted By davidwright2000
Replies: 15
Views: 974
Of course. And don't forget that some exposures are perfect - completely round stars. Astrotracer has to be doing something.

---------- Post added 06-19-20 at 08:48 PM ----------


Well, I can only choose what I'm given. So 350 mm. But once again, AT is erratic. Some exposures are good, many are not, and the ones ttat aren't good are bad in different ways.

---------- Post added 06-19-20 at 08:50 PM ----------


I'm mostly wondering why the results are inconsistant. If they were all poor in the same fashion, well, maybe it's something I can fix.

---------- Post added 06-19-20 at 08:53 PM ----------


Yes I have the field-flattener. And the soope is brand new. Shooting the field around Polaris (with AT off) gives perfectly round disks (or points for the faint ones) for the stars closest to the pole
Forum: Pentax K-1 06-18-2020, 04:41 PM  
Astrotracer consistancy with a 360 mm lens
Posted By davidwright2000
Replies: 15
Views: 974
This is a K-1. Heavy duty Oben tripod. I have a gear head - no sag after adjustment, but I only readjusted 2 times. Cam + lens is 8 pounds. M-51 was at 316 and 75 degress elevation. This whole series of exposures only took 20 minutes.

But I don't see how any of that matters (except crossing the zenith, which I didn't). Wherever I point, I should see consistant results, whether they be good or bad. At least that is what I expect....

I forget to mention that, looking at the exif data, I see the 'photographic direction' jumping around by up to 10 degrees.
Forum: Pentax K-1 06-18-2020, 01:54 PM  
Astrotracer consistancy with a 360 mm lens
Posted By davidwright2000
Replies: 15
Views: 974
I haven't seen this topic discussed in existing threads. The problem I am seeing is that, shot-to-shot, I see huge variations in the tracking accuracy. In the summary image attached, I'm taking consequetive 20 sec exposures with a ZenithStar61 360mm refractor. Each image of the 36 I took (of an area near M-51, which is currently near the zenith) shows a 200% crop of a region near the center of each image.

Because of a peculiarity in the way that photoshop brings in a group of images, the image start in the second column going down, then 3 column and so on. The final 6 exposures are in the first column.

As you can see, the tracking errors change drastically shot to shot.

Maybe this happens all the time, and is only noticible at longer FLs? I've gotten good results at 135 mm.

The focus seems to change, but I doubt that is what is actually happening, If I shoot the region about Polaris (astrotracer turned off), the star shapes a perfect and the smallest stars are about 1 pixel across.
Forum: Digital Processing, Software, and Printing 08-03-2019, 11:05 AM  
Pixel-shift bug in DCU 5.6.0?
Posted By davidwright2000
Replies: 7
Views: 787
Thanks for the comment. I have RT 5.2 installed, and have used it on occasion; more now since there are presets for pixel-shift. It's probably no surprise to you that I find RT hard to use, with poor or non-existant descriptions of the hundreds of parameters.

I'm probably doing something wrong, but I found the RT implementation of PS worse than DCU - colors muddier, result noisier, and most importantly, the sensitivity to motion too high (when I look at the map of pixels where motion was detected, presumably by intensity differences in the 2 green pixel values, many many are shown as having motion and therefore unsuitable for PS. It seems to me that DCU is more lenient in how much intensity difference is allowed.)

David
Forum: Digital Processing, Software, and Printing 08-01-2019, 10:44 AM  
Pixel-shift bug in DCU 5.6.0?
Posted By davidwright2000
Replies: 7
Views: 787
Thanks for the quick replies. I updated to 5.8.3 and that solves the problem (for now).
Forum: Digital Processing, Software, and Printing 08-01-2019, 08:32 AM  
Pixel-shift bug in DCU 5.6.0?
Posted By davidwright2000
Replies: 7
Views: 787
I always shoot tripod-mounted landscape images in pixel-shift mode, and process both in P-S and as a single image. If the motion artifacts are too much I use the single image, otherwise I use the single image to fix motion problems in the P-S image.

However, recently, DCU will not export either a jpeg or a tif file when I change the P-S parameter from 'as set on camera' to 'off'. The process window shows for just an instant, then vanishes. This happens with both my K-1 Mk I and K-70.

I have DCU 5.6.0 installed on 2 computers and the problem occurs on both.

I can open the PEF file in DxO photolab and process a single image from the raw file with that app.

Processing both P-S and a single extracted image used to work, and now it doesn't. Is this a known problem, and is there a fix?

David
Forum: Pentax K-1 04-02-2018, 01:59 PM  
Custom input focal lenght for astrotracer
Posted By davidwright2000
Replies: 8
Views: 1,318
Sorry - yes, of course the FL is necessary, in order to know how fast to move the sensor.

I tried shorting out the contacts with aluminum foil, but no matter how I tried covering the contacts, the cam never asked for FL, and the menu setting for selecting FL never enabled.

Others have said that the K-1 does not have this problem, but all I know for sure is that with my K-70, even with the latest firmware installed, I cannot set the FL for the OTA connected by a t-adapter.

David
Forum: Pentax K-1 03-31-2018, 11:09 AM  
Custom input focal lenght for astrotracer
Posted By davidwright2000
Replies: 8
Views: 1,318
I have a similar (but worse) issue - I can't set the FL at all when I attach a fully manual 'lens' using a t-adaptor. The 'set focal length' menu option is greyed out. And astrotracer doesn't work at all, so i'm guessing that this is because the focal length is 0.0.

It's not clear why astrotracer needs the FL at all, except for the estimate of max exposure time.

Astrotracer does work with my manual focus Rokinon 135 mm lens. The cam (K-70) asks for the FL when turned on.

David
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