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05-05-2018, 06:02 AM   #1
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Ogps1 vs SkyTracker etc.

Hi all,

I couldnít find anything by searching, so maybe itís been asked before, but I couldnít find it.

I started doing astrophotography last year and really enjoyed it, so Iím ready to invest in a way to make longer exposures. I have a k3 and too many lenses, though I want to likely use the sigma 8-16 a sigma 300 f2.8 and once released the Pentax 501.4 primarily. If Pentax releases the new apsc body itíll likely be moot, but I donít think thatís happening soon enough.
The question is do I buy the astrotracer or a motorized mount? The astrotracer is somewhat less expensive and people have gotten excellent results, but I hear it can be finicky and longer lenses can be limited. What says the crowd?

Cheers

MEB

05-05-2018, 06:16 AM   #2
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Have you looked at this info

Pentax O-GPS1 reviews - Pentax Camera Accessory Review Database

Pentax O-GPS1 GPS Unit Review - Introduction | PentaxForums.com Reviews

Astrotracer
This function controls the camera's image sensor by adjusting it in minute increments to allow for the earth's movement. This allows photos of up to 5 minutes to be taken at night without having star trails appear.

Basically, this turns the camera's sensor chip into the equivalent of a telescope equatorial mount although unlike a real mount which is unlimited in the amount of time it can adjust since the entire mount and telescope turns, the camera is limited to the amount of adjustment of the sensor and the time the object appears in the camera lens since the camera is stationary on it's mount.

The Astrotracer is not available on the Pentax K-01, 645Z, and 645D cameras.

Pentax O-GPS1 GPS Unit Review - Feature Overview | PentaxForums.com Reviews
05-05-2018, 06:22 AM - 1 Like   #3
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I've only got experience with using the O-GPS1 so it's not going to be complete advice from me - but here are my thoughts.

I used a 200mm Takumar lens with my K-3 to take images of Orion and Andromeda. The maximum exposure I could take with reliable results was 40 seconds with ISO800. At this kind of exposure, living in a area with significant light pollution, I still achieved excellent results that I am proud of. I think that the level of light pollution will ultimately help you make your choice. The O-GPS1 might be more than enough if you're in an area with low light pollution or are imaging bright objects. If you're imaging dim objects then the level of light pollution might be too high to capture any meaningful signal with even 40 seconds of exposure. You might need a proper tracker to get 2 to 5 minute exposures.

Of course, the price is a big factor so I would recommend buying an O-GPS1 to cut your teeth and maybe look to upgrade when you get more experience and if you really need something better.
05-05-2018, 06:23 AM   #4
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If you have an interest in astrophotography I would go with a robust equatorial mount. The tracking is better and more reliable and you avoid the effects of field rotation. The astroracer technology is fun but really limited to short exposures.

05-05-2018, 06:28 AM   #5
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You might want to look at this series:

Astrophotography Series Announcement - Articles and Tips | PentaxForums.com
05-05-2018, 07:14 AM   #6
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I second Pentax Syntax!

For less than twice the price of the O-GPS1, you can have a nice motorized tracking mount, if you put these two together:

Meade 41-7100-00 LX70 German Equatorial Telescope Mount & Tripod Excellent Cond 709942997125 | eBay

Meade LX70 Dual-Axis Drive System - 670011


If you are not quite sure how this all works, I suggest you find a local astronomy club. It will be full of folks who will be glad to help you get going.

For somewhat more, you can get something similar, but ready to go (you will still need to do a polar alignment): Explore Scientific FirstLight Exos-2GT Equatorial GoTo Mount with Tripod, White 812257016501 | eBay

(I have nothing to do with any of the above vendors, although I have bought stuff from Ebay seller scopehed1 and was quite satisfied with it.)

In the long run, I think you will find a conventional tracking system to be more satisfying than using the O-GPS1. It will work with just about any camera and lens that you have now or in the future.
05-05-2018, 07:51 AM   #7
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I second what AstroDave recommended. The Astrotracer feature tracks using the image sensor, which works well for shorter exposures and narrower fields, but it has problems with stars at the edges of wide field shots because moving the sensor can't compensate for the motions of stars in the center of the image and at the edges at the same time. Also, there is a set range of motion for the sensor before it runs into the limits that it can move (hence limiting the time of the exposure).

An equatorial mount doesn't have these limitations and will track stars right to the edges of a wide field shot (and for much much longer time periods). AstroDave's suggestion for the GoTo mount is great because it has interesting objects programmed into it's positioning computer (just a handheld widget), and almost with the press of a button, will "Go To" or center those sky objects once calibrated on a known object beforehand. All great features though at a bit more cost and with a bit more setup prior to going to work, but all worth it if you're into serious sky photography. That suggested mount is also more heavy duty and worthy of a camera/lens combination which you might use.

05-05-2018, 11:19 AM - 1 Like   #8
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The answer depends partially on how you'll be traveling. If you need to pack lightly when traveling by air or backpacking long distances, the O-GPS1 is very appealing. I recommend the tracking mount for the best results, though.

If you stick with astrophotography and move up to stacking (taking dozens of photos of the same dim object and processing to improve signal-noise ratio), the tracking mount will maintain aim on your target while the O-GPS1 requires re-aiming to keep a telephoto lens on target.

Any 300 2.8 lens will be fairly heavy, ruling out the tiniest tracking mounts. Get a mount large enough to use with a counterweight to balance the load. Here's an example, but I have no specific experience with this new model. SkyGuider<sup>TM</sup> Pro Camera Mount Full Package
05-05-2018, 11:34 AM   #9
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The two types of equipment differ. I have the O-GPS1 unit and it is compact for what it does.
05-05-2018, 04:10 PM   #10
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I'd get the iOptron SmartEQ Pro instead. Sure, it is 500 bucks, but it has go to and tracking, is easy to align, and can give great results. I started getting stuff that was decent within a short period of time.

Here's some examples taken with it between 200 and 420mm fl with both the K1 and K3. Of course I'd say to order it through the link here on the forums, but here it is at B&H iOptron SmartEQ Pro Equatorial Mount Kit with Hard Case 3200-HC


05-05-2018, 04:50 PM   #11
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For a small equatorial type tracker, the Sky Watcher is pretty good (see review below). It doesn't have a "go to" feature but does have an auto-track input which can be used with a separate device to stay on a target without the need for manual adjustments (only works on one axis though). Be careful if you buy because the basic unit may need some accessories for tripod use and heavier camera/lens combinations (counter balance) - added cost to basic unit. Nice small tracker intended for cameras without jumping into a full-blown equatorial mount.

Skywatcher Star Adventurer: Review | Phil Hart
05-05-2018, 05:15 PM   #12
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Thanks all, good food for thought. I suppose as with all things in life you have to pick your poison. I'm leaning towards a mount such as voiceofreason mentioned since I'll want to replace the K3 with either the new apse-c flagship or go K1-III in a year or two. Having the mount will let me use any camera. Don't suppose anyone wants to trade an adapt-all 300 2.8 for a tracking mount?
Guess it's time to save some pennies and get one for the summer. I'm fortunate enough to have a cottage located ~700 km north of Toronto, so there's very little light pollution to worry about.
05-06-2018, 02:10 AM - 1 Like   #13
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The O-GPS1 is a bargain for what it allows you to do compared to untracked photos. ~15 seconds max with untracked 24mm, and upwards of 4 minutes with ast`rotracer. There is a great deal that can be done with it. It gives good performance for wide field work like the milky way, and the larger DSO. You can also use heavy OTA with modest focal lengths that would not be suitable for the more affordable tracking mounts. There is a lot of crossover with what you can do with the gps vs an affordable tracking mount.

If you want to use a larger telescope to capture smaller and fainter DSO, a heavier duty and more expensive tracking mount is needed. The more affordable tracking mounts are best for longer focal lengths with smaller apertures and longer exposures, or images needing many shots stacked and the time savings from repositioning adds up.
05-06-2018, 03:14 AM   #14
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welcome to the forum, bcp38

nice informative and helpful first post
05-06-2018, 04:46 AM   #15
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Has anyone had success using the ogps with a 300mm lens?
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