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Author Topic: Pentax 645z Astrophotography Using the iOptron SkyTracker  (Read 22012 times)

DaveCurtis

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #20 on: October 11, 2014, 02:41:47 am »

Beautiful Dave! That is really an interesting option you shared here.

Did you use a narrow band 12nm filter?


No filters used. The QHY 8pro is a colour camera APS-C ccd and no filters used with this image. Similar results can be obtained with a modified DSLR.

My next camera will be a astro mono with a computerised 8 filter wheel so I can shoot LRGB and 5nm narrow band.  Well that's the plan  :D

I use PixInsight to do the processing to the .fits files.



Dave
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jjj

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #21 on: October 12, 2014, 02:59:33 pm »

Andromeda is high on my list. Regrettably we've now have had 10 cloudy nights in a row
Feels like 10 months in a row here. Ironically I moved to Sheffield to study Astronomy.
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jjj

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #22 on: October 12, 2014, 03:02:06 pm »

There are places in Japan with very little light pollution, but winter time is probably the best and those get pretty cold at night (rarely warmer than -10C).
Warmth and good shooting conditions tend to be mutually exclusive.  :-\
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michael

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #23 on: October 12, 2014, 05:49:49 pm »

This coming evening is the first really clear night here in a couple of weeks. There is also no moon, at least until moonrise at 9:50pm. Astro darkness begins at about 8:30pm. It's not even that cold yet.

So, I should have near perfect conditions for deep sky shooting for about 90 minutes. We'll see.

Michael


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jjj

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #24 on: October 12, 2014, 07:34:23 pm »

Good luck with that. Astro photography requires even more patience that normal photography.
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Torbjörn Tapani

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« Reply #25 on: October 12, 2014, 10:46:43 pm »

Very true. Not at all uncommon to have one shot at capturing an event. Then you find that you somehow nudged the focus ever so slightly. Then when you are all set again frost on the bulbous front element... Oh well. I can try the Geminids again this year. But then it's a very bright moon... Sigh.
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Fine_Art

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #26 on: October 13, 2014, 01:53:48 pm »

Another really useful article on LuLa.

I have been doing mostly the moon with a 10" dob. An option is to take many short exposure shots then use software to grade then stack the best images. The software can compensate for rotation as well as tracking.
You still need a solid mount.
You still need a good (preferably FF) chip.

The free registax is worth trying out. You can always move up the software food chain later if you really enjoy being out at night.

The camera in the article is obviously top of the line for this work. You can also use a smaller chip if you rely on a big scope to gather the light. For example I can shoot the moon on APSC ISO100 at 1/500th ETTR (Sony A55 with mirror flipped up) or the same 1/500th with the Nikon D600. Of course the 10" mirror is gathering the light.

Using a regular lens, you already know what exposure you need for the black sky. With a big scope, the Milky way, ISO1600 which is very clean on D600; you can shoot 1/100 to 1/25th (whatever you like really) then let the software super sample the frames to take you to ETTR. A good tracking mount for a big scope gets pricy.

Whatever gear you try, the limitation will likely be your tolerance for cold nights or hot summer mosquito nights.

Edit: link to registax align page - http://www.astronomie.be/registax/previewv6-1.html
« Last Edit: October 13, 2014, 02:11:50 pm by Fine_Art »
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NancyP

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #27 on: October 13, 2014, 02:37:12 pm »

That is really wonderful, Dave.
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Telecaster

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #28 on: October 13, 2014, 03:44:11 pm »

I really like Michael's Andromeda galaxy photo, taken with the relatively simple Pentax Z + 120/4 lens + SkyTracker outfit. This is one good way to get started with astrophotography IMO. I'm seriously thinking about getting a SkyTracker myself and doing some longer-exposure astro stuff this winter with an A7r + Zeiss 100/2 (Y/C mount) combo. Keep it compact & light.

-Dave-
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michael

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #29 on: October 13, 2014, 04:11:14 pm »

Dave,

You beat me to mention that I just published a Phlog entry today titled Andromeda.

It includes a downloadable 3MB version of the image that people can print for themselves.

Michael
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Rick Popham

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #30 on: October 13, 2014, 06:28:59 pm »

Dave,

You beat me to mention that I just published a Phlog entry today titled Andromeda.

It includes a downloadable 3MB version of the image that people can print for themselves.

Michael


Thanks, Michael!  It'll be interesting to print this.
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Torbjörn Tapani

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #31 on: October 13, 2014, 07:16:45 pm »

There is a happy medium ISO that does analog gain but don't decrease dynamic range so much. You want to be able to differentiate between values in dim objects (andromeda) without saturating bright objects (stars) so much. With a D800 there is little point going above ISO1600, you can do the rest of the scaling in post. It would be interesting to see what the 645Z sensor does with increasing ISO. With stacking you can increase S/N ratio in dim parts without saturating stars so much or at all. Then it is possible to push the resulting 32-bit file a lot more in post.
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michael

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #32 on: October 13, 2014, 08:29:43 pm »

I've downloaded Nebulosity (I use  Mac) and as soon as I have clear skies again will experiment with stacking. Unfortunately, the forecast here is for 5 straight days of rain.

Michael
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jjj

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #33 on: October 14, 2014, 12:13:14 pm »

I've downloaded Nebulosity (I use  Mac) and as soon as I have clear skies again will experiment with stacking. Unfortunately, the forecast here is for 5 straight days of rain.

Michael
I just spent two days standing in the damn stuff and discovered my waterproof socks are not what they claim.   :-\
Currently looking for waterproof shoes and 3/4 shorts for biking and they are mostly not in stock yet. Apparently not quite the season!!??   ???
A bit dumb as it can rain so much it floods at just about any month of the year in the UK, July being particularly bad in recent years and October is usually when it's both cold and wet and when you would expect Winter ear to have been in for a while.
Though we did just have the driest September ever, preceded by the wettest Jan-July ever.
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BernardLanguillier

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #34 on: October 20, 2014, 09:54:15 pm »

First attempt this Sunday with the Astrotrac TT-320X-AG.



I found locating Polaris easier than I thought it would be thanks to the iPhone app Starmap Pro. It did validate what I thought was Polaris and made the whole experience less "stressful".

I found it a bit challenging to adjust the position of Polaris in the Polar scope with my RRS large ball head, but it can be done.

I used the Sigma 35mm f1.4 Art at 2.8 on the D810. With a 4 mins exposure at ISO 1600 I don't see much of a trail behind stars, so things seem to work fairly well. Beginner's luck I guess.

Cheers,
Bernard
« Last Edit: October 26, 2014, 06:54:29 pm by BernardLanguillier »
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Telecaster

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #35 on: October 21, 2014, 01:28:17 am »

First attempt this Sunday with the Astrotrac TT-320X-AG.

Looks good. How are the overall seeing conditions where you're at? I can get away from the worst of the Detroit area's light pollution with a 30-mile drive northwest, but from my backyard—where I'd prefer to set up in colder weather—there's an annoying amount of "base fog" to contend with.

-Dave-
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Bart_van_der_Wolf

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #36 on: October 21, 2014, 03:13:12 am »

First attempt this Sunday with the Astrotrac TT-320X-AG.
[...]

I found it a bit challenging to adjust the position of Polaris in the Polar scope with my RRS large ball head, but it can be done.

Hi Bernard,

That's why a geared head is often used for polar alignment, and another (ball-)head for camera positioning. But the image seems to look good. So that part of the challenge seems to be covered, now comes the challenge to practice on locations with interesting landscapes.

Cheers,
Bart
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BernardLanguillier

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #37 on: October 21, 2014, 08:39:25 pm »

Looks good. How are the overall seeing conditions where you're at? I can get away from the worst of the Detroit area's light pollution with a 30-mile drive northwest, but from my backyard—where I'd prefer to set up in colder weather—there's an annoying amount of "base fog" to contend with.

Dave,

Tokyo is totally useless. I was up north and it seems excellent. I was very tired after an intensive day of shooting and settle for an easily accessible location accessible on foot from the lodge with some lights in the vicinity, but a 1 km drive would have taken me to an apparently totally dark location. Even where I was the milky way was visible with the naked eye.

Cheers,
Bernard

BernardLanguillier

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #38 on: October 21, 2014, 08:44:37 pm »

That's why a geared head is often used for polar alignment, and another (ball-)head for camera positioning. But the image seems to look good. So that part of the challenge seems to be covered, now comes the challenge to practice on locations with interesting landscapes.

Bart,

Yes, I was aware it was not the perfect head, but I use the ball head for my general shooting with pano gear. After all these years of hesitating, I may have to finally invest in an Arca cube C1 I guess. ;)

You are totally right, I need to improve on 2 axis:
- Identification of suitable landscape spots. There was a great one nearby I was considering, but a day light recon revealed that trees obstruct Polaris...
- Better knowledge of the sky (what to look for, seasonal aspects,...).

Cheers,
Bernard
« Last Edit: October 22, 2014, 03:52:23 am by BernardLanguillier »
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Bart_van_der_Wolf

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Re: Pentax 645z Astrophotography Using the iOptron SkyTracker
« Reply #39 on: October 22, 2014, 03:38:01 am »

Bart,

Yes, I was aware it was not the perfect head, but I use the ball head for my general shooting with pano gear. After all these years of hesitating, I may have to finally invest in an Arca cube C1 I guess. ;)

While nice engineering, it's probably overkill for the purpose. Many people who use the Astrotac report success with a Manfrotto 410 Junior Geared Head (rated for a 5kg payload). I have a Manfrotto 405 Geared Head (rated for a 7.5 kg payload) with a Heynar Arca Swiss Clamp replacement, which may be overkill for lighter camera/lens combinations but still very much more affordable than a 'cube'.

Quote
You are totally right, I need to improve on 2 axis:
- Identification of suitable landscape spots. There was a great one nearby I was considering, but a day light recotrees obstruct Polaris...
- Better knowledge of the sky (what to look for, seasonal aspects,...).

I agree there is a learning curve involved, and practice makes perfect, but there will remain to be challenges. No visibility on Polaris is a big issue, but then we may also combine/composite two images. One image with attractive foreground, and one with unobstructed sky (from a nearby location if we want to stay true to the truth).

Actually getting the images in the first place is obviously the first step of creating beautiful final images, it's a process.

Cheers,
Bart
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