Astrophotography with the OM-1 and the Oly f/5.0-6.3 100-400mm

Atanarjuat wrote:

Hello, long time reader and first time poster here.

I have a question regarding exposure times for astrophotography with your setup. I also live in a populated area (Bortle 8). I've attempted long exposure photos of the sky with my Panasonic 100-300MM II. I get almost completely washed out and over exposed images of even relatively clear sky (no clouds) with exposures over 30 seconds @ f/5.6, ISO 400.

How did you manage individual 150-second exposures in your 33 image stack? I don't feel like I could get even close to that. Curious what an individual, unprocessed light frame looks like before stacking and calibration with dark and flat frames.

Part of what made this possible, I think, is that Orion was in the southern sky when I took the images.  From my rear deck, the southern sky is less light polluted than the northern sky, in fact, quite a bit less to my eye.  And all of the sites I've seen that provide this kind of information classify my city as Bortle 8.  However, one site, which I've never been able to find again, provided fine-grained information, and my house seemed to have a Bortle 6 sky.  And stacking and post processing seem good at removing the light pollution too.  As requested, I'm including one of the 150-second light frames below.

Al

One 150-second light frame.

ABCMO wrote:

Bialykot wrote:

Thank you (and another great picture). Good to know the GTI can handle the 100-400 plus OM1 payload. I have a GTI tracker on order (and already have the OM1/100-400) but am completely new to Astrophotography, although keen to try. Auto guiding might be of interest at a future date if I take to the new hobby, but want to keep costs low for the moment. But you’ve certainly proved that the kit is capable of good results (in the right hands of course), so that’s very encouraging.

Thank you for commenting positively about the Pleiades image. Because you have a GTi on the way, I thought I should share a couple of things I have learned that might help you avoid some significant problems with it.

First, never, I repeat, never use a planet to perform any of the star alignments one performs for maximum accuracy before using the GOTO capability. I thought I had a defective unit because during the three-star alignment, on the second or third object, the GTi would slew and end up pointing the camera and lens toward the ground! I finally called my vendor, High Point Scientific, for techinical support, and the advisor I spoke with figured out what was causing my problem when I mentioned that I had been using Jupiter and Mars as objects in the star alignments. He told me never to do that, and that the problem wasn't limited to the GTi as it was a general problem with these kinds of equatorial mounts. He said the manuals don't say anything about this, but he has experience with several different mounts, and using planets for the alignment is trouble. Big trouble. I had used those two planets because they are so bright and would be easier to identify on the camera's back screen after the GTi would slew to them. The target object needs to be identified because although it may be in the frame, often it is necessary to use the SynScan software controls to place the object in the exact center of the frame. Sometimes the object will be almost exactly centered, but not always. So only use stars for star alignment even though the software will list Jupiter or Mars right now at the top of the list of available target options.

Second, and again the manual is silent on this point, the mount has two locations on the front for attaching the counterweight shaft that holds the 5.5-pound weight used to balance the camera-lens assembly. One location is for middle and fairly high latitudes and the other is for lower latitudes. What I discovered is that using the attachment point for the middle latitudes--I'm at 39 degrees north--the counterweight must be positioned so high on the shaft that it will come into contact with parts of the mount during slewing. The solution is to use the attachment point for lower latitudes. The counterweight must still be positioned high on the shaft, but it will be well out of the way and not come into contact with any part of the GTi during slewing. This is not just me suggesting this solution, but there are at least two video tutorials on YouTube that note this problem and recommend this solution, one of them being from High Point Scientific itself. The advisor I spoke with also endorsed this solution. This entire problem is caused because the OM-1 and 100-400 lens together form a relatively light combination, around 3.8 pounds. Even when I add a vixen dovetail plate and my guide scope and camera along with lens warmers, my total payload comes in around 5.6 or 5.7 pounds, and the GTI's maximum load is 11 pounds.

I hope these two recommendations will save you from having several fruitless nights under the stars. And good luck as you begin this journey.

Al

Hey - thanks for those tips!  I didn’t know the issues about the counterweights, so will heed your advice.  I guess the ‘planets” alignment mistake is easily made, but when you think about it, the planets have totally different ‘movement’ (relative to the earth) from the stars. There’s a bit of a waiting time for the GTI, so I’m hoping I’ll have plenty of opportunity to watch some YouTube tutorials and learn a bit about tracking and especially post processing.  Thanks again.

Thanks for the sanity check. That shot looks good for something SOOC. I'm getting started in astrophotography with a Panasonic G95 and Panasonic 100-300MM II 4.0-5.6 lens mounted to a iOptron SkyTracker on a solid tripod base from the roof of my building.

I'm not sure of the methodology used to determine Bortle values, but I suspect the values on these websites must be averages that don't account for local variation.

RobPNth wrote:

ABCMO wrote:

Atanarjuat wrote:

Hello, long time reader and first time poster here.

I have a question regarding exposure times for astrophotography with your setup. I also live in a populated area (Bortle 8). I've attempted long exposure photos of the sky with my Panasonic 100-300MM II. I get almost completely washed out and over exposed images of even relatively clear sky (no clouds) with exposures over 30 seconds @ f/5.6, ISO 400.

How did you manage individual 150-second exposures in your 33 image stack? I don't feel like I could get even close to that. Curious what an individual, unprocessed light frame looks like before stacking and calibration with dark and flat frames.

Part of what made this possible, I think, is that Orion was in the southern sky when I took the images. From my rear deck, the southern sky is less light polluted than the northern sky, in fact, quite a bit less to my eye. And all of the sites I've seen that provide this kind of information classify my city as Bortle 8. However, one site, which I've never been able to find again, provided fine-grained information, and my house seemed to have a Bortle 6 sky. And stacking and post processing seem good at removing the light pollution too. As requested, I'm including one of the 150-second light frames below.

Al

One 150-second light frame.

Did you use any narrow band filters on the lens?

No narrowband filters.  All I used was a good B&W clear protective filter on the lens.

Al

ABCMO wrote:

RobPNth wrote:

ABCMO wrote:

Atanarjuat wrote:

Hello, long time reader and first time poster here.

I have a question regarding exposure times for astrophotography with your setup. I also live in a populated area (Bortle 8). I've attempted long exposure photos of the sky with my Panasonic 100-300MM II. I get almost completely washed out and over exposed images of even relatively clear sky (no clouds) with exposures over 30 seconds @ f/5.6, ISO 400.

How did you manage individual 150-second exposures in your 33 image stack? I don't feel like I could get even close to that. Curious what an individual, unprocessed light frame looks like before stacking and calibration with dark and flat frames.

Part of what made this possible, I think, is that Orion was in the southern sky when I took the images. From my rear deck, the southern sky is less light polluted than the northern sky, in fact, quite a bit less to my eye. And all of the sites I've seen that provide this kind of information classify my city as Bortle 8. However, one site, which I've never been able to find again, provided fine-grained information, and my house seemed to have a Bortle 6 sky. And stacking and post processing seem good at removing the light pollution too. As requested, I'm including one of the 150-second light frames below.

Al

One 150-second light frame.

Did you use any narrow band filters on the lens?

No narrowband filters. All I used was a good B&W clear protective filter on the lens.

Al

Shock! Horror!

How could you possibly get such a good result with a protective filter on? Especially with astro (reflections!!) and a super tele lens... what witchcraft is going on here?

(Just having fun at the no filter brigade expense.)

glassoholic wrote:

ABCMO wrote:

RobPNth wrote:

ABCMO wrote:

Atanarjuat wrote:

Hello, long time reader and first time poster here.

I have a question regarding exposure times for astrophotography with your setup. I also live in a populated area (Bortle 8). I've attempted long exposure photos of the sky with my Panasonic 100-300MM II. I get almost completely washed out and over exposed images of even relatively clear sky (no clouds) with exposures over 30 seconds @ f/5.6, ISO 400.

How did you manage individual 150-second exposures in your 33 image stack? I don't feel like I could get even close to that. Curious what an individual, unprocessed light frame looks like before stacking and calibration with dark and flat frames.

Part of what made this possible, I think, is that Orion was in the southern sky when I took the images. From my rear deck, the southern sky is less light polluted than the northern sky, in fact, quite a bit less to my eye. And all of the sites I've seen that provide this kind of information classify my city as Bortle 8. However, one site, which I've never been able to find again, provided fine-grained information, and my house seemed to have a Bortle 6 sky. And stacking and post processing seem good at removing the light pollution too. As requested, I'm including one of the 150-second light frames below.

Al

One 150-second light frame.

Did you use any narrow band filters on the lens?

No narrowband filters. All I used was a good B&W clear protective filter on the lens.

Al

Shock! Horror!

How could you possibly get such a good result with a protective filter on? Especially with astro (reflections!!) and a super tele lens... what witchcraft is going on here?

(Just having fun at the no filter brigade expense.)

👍

Al