[seti_v2]

Link to full res and more info if anyone is interested. Bi-Color Melotte 15 (seti_v2) | AstroBin

---

Last edited by seti_v2; 10-24-2014 at 06:12 PM.

[SirTomster]

I took this picture of Orion's sword this morning during the lunar eclipse.
Camera: K-5
Lens: SMC Pentax-DA 55-300mm F4-5.8 ED
O-GPS1 (Astrotracker), 60 seconds, f8, ISO 1600, 300mm.
Used Lightroom 5 to crop a bit and adjustments to remove light pollution.

So how good is the O-GPS1 with a zoom lens. Can you get 4 1/2 minute shots even at 300mm or is it more limited?

I am looking into getting the O-GPS1 or another type of SkyTracker to take even longer shots.

[interested_observer]

So how good is the O-GPS1 with a zoom lens. Can you get 4 1/2 minute shots even at 300mm or is it more limited?

I am looking into getting the O-GPS1 or another type of SkyTracker to take even longer shots.

Morning Tomster,

You certainly will not be able to get 4.5 minutes of tracking with a 300mm. 60 seconds is about as long as you are really going to be able to get. The limit for the longer focal lengths is caused by the angle of view of the lens (the longer the focal length the shorter the tracking time), along with the amount of movement the sensor is allowed. If you want longer tracking times, you can take successive shots each at 60 seconds each and then stack them. That will help a bit with the accumulation of sensor noise and built up heat.

[maxxxx]

So how good is the O-GPS1 with a zoom lens. Can you get 4 1/2 minute shots even at 300mm or is it more limited?

I am looking into getting the O-GPS1 or another type of SkyTracker to take even longer shots.

I think you'll be better off with a dedicated tracker. The O-GPS1 is nice but it's pretty limited.

[djseeram]

So how good is the O-GPS1 with a zoom lens. Can you get 4 1/2 minute shots even at 300mm or is it more limited?

I am looking into getting the O-GPS1 or another type of SkyTracker to take even longer shots.

This is what pentax claims: Link Scroll to the bottom of the page.

Declination 90 degree is pointing to pole star and dec 0 is pointing to equator.

[stanzhou]

I have both O-Gps and iOptron skytracker
o-gps is pretty good and extreme lightweight for superwide angle milky way
when it comes to wide field astrophotography like 200mm or 450mm
it only lasts less than 45s, mostly 30s

This Rho Ophiuchus cloud was taken with pentax smc M 50 1.4, 60+120+240s, on iOptron Skytracker, stacked with PS6 median stack @ISO1600 f2.8;


This summer milky way pano was taken with pentax SMC DA 18-55mm @ISO800 f3.5 180s, on iOptron Skytracker, 5 subframes merged in PS


This widefield of Lagoon nebula(M8) and triffid nebula(M20) was taken with pentax da 50-200mm @ISO3200 F5.6 180s, on iOptron skytracker

Photos below were taken with Pentax O-Gps

Taken with Samyang 14mm 2.8, ISO1600, 60s, so far so good at wide angle.


Taken with pentax SMC M 50mm 1.4, @f2.4; ISO1600, 120s, still good enough for a hotshoe tracker


Taken with takumar 200/4 @ f4 ISO1600 45s each, 28subframes stacked in DSS, although exposure was decreased to 45s and even 30s, star trail is easy to observe without any zoom in.

In conclusion, I would choose OGPS for Milky way with landscape purpose because of lightweight and good accuracy of tracking at wide angle to short-tele. But anyone are willing to step further in astrophotography (taking wide field astrophotography from 70mm or above), I would definitely recommend a serious tracker. Thanks for reading.

[Stone G.]

Thanks for sharing your interesting pictures with us stanzhou.

But anyone are willing to step further in astrophotography (taking wide field astrophotography from 70mm or above), I would definitely recommend a serious tracker.

I can't say that I totally disagree with you, because I would also certainly not consider the O-GPS1/Astrotracer as a real replacement of a (good) equatorial tracking platform. Still, one should not totally dicard the O-GPS1 for the longer lenses. With today's sensors you can have great fun and get the "thrill of discovery" using the O-GPS1/Astrotracer for just some 20-40 seconds exposures even with lenses in the 200-400mm range:


Planetary nebula M27, Dumbell Nebula, in Vulpecula. Image taken with Pentax K-5 and smc PENTAX-DA* 1:2.8 200mm lens.
Five 20 second exposures at f/3.5 and ISO 1600 stacked in DSS and post-processed in PhotomImpact X3
Click to see non-resized 100% crop.

[seti_v2]

NGC1499 California Nebula.

Taken over two nights.

22 x 900" ISO800 Pentax k5 through 6nm H-alpha filter
Orion 120mm f5 refractor
NEQ6 mount

[Suhndog]

Can the O-GPS be updated, or does it not allow firmware updates?

[Stone G.]

Can the O-GPS be updated, or does it not allow firmware updates?

Firmware for the O-GPS1 js embedded in the camera firmware - so just have your camera updated.

As far as I recall, there have been just two updates for the K-5 specifically mentioning the O-GPS1. First was to allow operation at all and second was some sort of 'general stablity issue' if I remeber correctly.

[Suhndog]

Thanks, Stone G.

Since I will only have funds to either buy an O-GPS1 and appropriate lens, or upgrade my 10" DOB to track for astro imaging, I'm trying to determine which way to go.

Marc

[seti_v2]

Tracking a 10" DOB for imaging is going to be very demanding. What did you have in mind if I may ask?

[Suhndog]

Well, there are some pre-made EQ platforms available, or kits, etc. but they are pricey, and my funds are limited. I had seen some remarkable images produced using the O-GPS1, and far less expensive. I don't mind doing post processing, so I most likely will get the O-GPS1, and a good lens now that I think about it..

As such, what would be a good lens(s) choice for my K5?

[SirTomster]

Well, there are some pre-made EQ platforms available, or kits, etc. but they are pricey, and my funds are limited. I had seen some remarkable images produced using the O-GPS1, and far less expensive. I don't mind doing post processing, so I most likely will get the O-GPS1, and a good lens now that I think about it..

As such, what would be a good lens(s) choice for my K5?

What kind of shooting do you plan to do with the O-GPS1 route?

Do you want wide angle or something with Zoom?

I also have decided to get the O-GPS1. Since I am initially interested in wide frame images with some landscape feature. I currently own the Rokinon 14mm F2.8 Manual Lens. Only $300.
Here are a few images I took with just 30 seconds exposure and some post processing in Photoshop.

I cannot wait to see what I can get with the O-GPS1.

[Stone G.]

Beautiful pictures SirTomster - I wish I had that kind of a sky!

And in continuation to our answer to Suhndog: Vintage MF-lenses can be used for atro photography but the probelm with them can be, that many of the wider ones (say, from 50mm FL and shorter) suffer from annoying coma. Therefore, a modern, aspherical design like the Samyang/Rokinon seems a better choise.

If you on the other hand favour the longer focal lengths (300mm being about the sensible and 200mm the "safe" upper limit in O-GPS1 context) there are many cheaper Takumar, smc Pentax, Tamron adaptall-2 etc. lenses available). You can see my results with various lenses here:


DSLR Astophotography: Astrotracer Images with Pentax GPS Unit O-GPS1