LX200 Imaging and 30 Sec Alt/Az limit
Posted 07 April 2013 - 03:45 PM
As I continue to learn and read I always have more questions... Having had several LX200's and having read many posts / articles on imaging, clearly at some point one should use a wedge with fork mounted scopes and I did obtain a wedge but would like to fulfill and learn more using alt/az still mainly because it is easier for me to move around and setup and once I feel I am good there I will go to polar.
My problem is I always read about an approx. 30 sec limit in exposures in Alt/Az with an LX200, but on all of my LX's I cannot get an 8 second exposure without the stars starting to "trickle" in the image, even if the object will stay centered for an hour more than 1 or 2 seconds and everything breaks down... I do not know what this is, when I hear I should be able to take up to 30 second exposures in alt/az... I have ran the training and used other tips before and same result. This seems to be the case about 1/2 way up or close to meridian so I am at a loss and could use some pointers... Please no "just use the wedge answers" as I will use the wedge when I can, but in the past even with the wedge I had similar issue's with anything longer than a second or 2... so would like to master alt/az.
as always any and all help suggestions greatly appreciated.
Posted 07 April 2013 - 04:07 PM
I know you don't want to discuss the wedge right now, but I was like you and tried to learn as much as I could in Alt/Az mode. I finally gave up and spent one whole night just getting the wedge alignment so I was happy with it and left everything set up for the next night. I was shocked at how much better my pictures were, right up until my camera died. I have a new camera on order, and this summer I will not consider anything other than a visual night in Alt/Az mode.
Posted 07 April 2013 - 04:11 PM
But seriously, what could be causing the problems. Wind sometimes can be a culprit. Do you have a remote cable hooked up to the camera? What kind of camera? Make sure you are not touching the telescope when taking the picture.
Their could also be periodic errors - you might want to correct for that.
Another trick if you have some vibration problems once you snap the exposure is to cover the front of the scope (do not touch it!) and remove after a few seconds - then cover and then end the picture.
Of course a guide scope can help a bit too, but best in equatorial mode.
Right now I am not guiding or anything, nor special processing, with my LX200 and won't get fancy until my LX850 comes in, however you can take some simple nice pictures with 30 second exposures or less with your LX200. Check out http://pinterest.com/spacetravelerx/ for some examples...
Posted 07 April 2013 - 04:24 PM
Attaching an image of M13... the stars "doubling" on the edges happen almost immediately... I am using Meade DSI, envisage... more than 1 second or so and this is what I get... I have bad light pollution and have no clue what I am doing but feel like I could probably get some satisfactory images if I could lick this problem...
Posted 07 April 2013 - 04:30 PM
I am probably going to start an uproar here…. So just hang on if you can.
I too like the Alt/Az world. My LX-200®GPS (8”) is pier mounted in a back yard observatory. Virtually, all of my observations are “imaged”. I use an SBIG ST-8300-M. My standard is a stack of 5 or 6 “frames”, each with 2 minutes exposure. Yup !! I said 2 minutes, and in Alt/AZ.
And I will add that usually, I image with the SBIG set at “Half”, which boils down to high magnification and small FOV. “Magnification” calculates to about 176x [ 2x(2000/22.5) ] which is 2x( (focal length) / (diag of ccd chip) ). This value is confirmed via Plate Solves on lots of images. The resultant FOV for the average image is about 16x12 Arc Min.
There are several important points that need to be addressed to make this work.
1. The mount must be VERY steady. Mine is pier mounted (Not tripod mounted).
2. The “balance” of the mount must be checked daily, and any change in configuration requires re-balancing (easy to do).
3. You MUST guide ( Yup…. Guide in Alt/Az !!) It works. My guiding is done with an 80mm EDAPO mounted piggyback on the LX200. On that configuration, I use a Orion StarShoot Autoguider camera (ST-4 output to the Meade).
Do I have problems ?? Sure. We all do.
But…. You must decide what you are trying to “get” in your images, and what you are going to do with them. I image everything in Mono. Not interested in color. My images form my observation “logs”. I don’t like to write descriptions, or sketch. I am willing to accept some small elongations and less than perfect images.
Would you like to see some of my images. My obersation “logs” are all on my website. You can find it here: http://az-douglass.net/astronomy . Check out the “Recent Images”, “General Observations”, and if you really want to see more, then the “DaHut” projects. “DaHut” is what I call the observatory.
I just (almost) completed a project, imageing the 40 galaxies from the Messier group. I have imaged them from “DaHut” (Tempe, AZ ), and then re-imaging them from a Very Dark Sky site. I prepared observation sheets with both images to show the effect of observing in light polluted areas (such as Tempe). That project can be found on “DaHut Projects” page, down at the bottom, or you can simply go here:
You can click on the dark sky site observation, or the comparison image (shows both).
Check it out, and see what you think. Let me know if you have any questions.
Posted 07 April 2013 - 06:09 PM
as always any and all help suggestions greatly appreciated.
Even if it's not what you want to hear?
The issue is setup time. Look at my website to see the extent I have taken that to.
Have you looked at options that will reduce setup times? If you set up in the same spot all the time there are some options that would let you set up with a wedge in almost the same time it is taking you to set up in Alt Az.
If you think you will eventually go the wedge route then you may well be doing nothing more than wasting your time trying to get the most out of Alt Az.
Posted 07 April 2013 - 06:42 PM
1. For imaging, EQ Mounts are Superior to Alt/AZ. Hands down. No argument. My maximium exposure in Alt/AZ is 2 Min. It would be nice to be be able to go longer.
2. The Azimuth, and the Alt of the target enter into play. Dead on North or South, and I really have a 90 Sec limit. Higher than 65 Degrees, and the same applies. Those are factors I deal with.
3. My original intent, was to put a wedge on my pier. Unfortunately, I did not calculate everything out. The pier is a hollow 4" square steel tube (thick). But with the wedge, I had "ringing". I fixed most of that by filling the tube with sand. But there was still minor movement, which is NOT good when trying to image. With the LX200 mounted in Alt/AZ, all of that went away.
Before the "DaHut", I was using the tripod method. And yes, there, the practical limit was 30 seconds. I "learned" after the pier, about balancing, and guiding. Put it all together, and like I say.... I get 2 minutes. Works for me !!
My "travel" mount is a Celestron CG5-GT, with a 6" SCT for an OTA. That, of course, is an EQ Mount. If I were to change to an EQ configuration at home, I would remove the LX200, and replace it with a true EQ (Celestron CG). Much easier to align, maintain, and operate.
- bbmiller likes this
Posted 07 April 2013 - 07:00 PM
Posted 07 April 2013 - 07:20 PM
I guess it all depends on the location.
Here in New Mexico, I leave my telescope (10"LX200 Classic) in the court yard for up to 7 days, running 24/7. It maintains its alignment/goto knowledge the entire time without a problem. This is with the Superwedge, but I assume the same could be said for alt-azimuth mode. The key with my scheme is I align once and I am good for up to a week.
Mind you I can get away with this because I am in a dry climate and it is clear for long stretches. Any rain, heavy dew, etc, you will have to bring the scope in and out or provide a good protective system.
And yes, I have to change the viewing coordinates of my scope every few hours so it does not go around and round!
Now - if you keep taking off and putting on the telescope you will have to realign every time.
And yes - there is an observatory in my future...
Posted 07 April 2013 - 07:40 PM
Posted 07 April 2013 - 08:11 PM
The wedge should be fairly easy to align. Once latitude is set and if always at the same location you are all set with it. Then you merely point the tripod pretty close to north and the adjustment is easy from there following the steps on the hand controller.
So in summary polar align for a wedge mount:
-- Set up tripod with wedge (I have mine always attached) and point generally north (maybe even mark on ground some how for future ref).
-- Make sure latitude is set for your location. (you should keep bolts lose to adjust alt-az on wedge)
-- Set the RA to 0 and DEC to 90 per controller. Hit enter...
-- Align on Polaris. Likely only need to adjust azimuth.
-- Secure all bolts - make sure still aligned on Polaris.
-- Hit enter
-- Line up on selected star.
-- You are golden. Do a few more for more precise alignment.
BTW - you might want to consider getting a SkyShed POD. They are an excellent option for a low cost observatory. http://www.skyshedpod.com/
Posted 07 April 2013 - 08:19 PM
This is the last photo I took before my camera died. I cropped it to get under the 200k limit, but otherwise this is an unedited shot of M13 that I took for 30 seconds. I did not have a chance to take dark frames so hot pixels can be seen. This photo was taken when M13 was almost directly overhead so it would have been a disaster in Alt/Az mode, but this was my first and only night so far taking pictures with the wedge.
Posted 07 April 2013 - 09:25 PM
The M13 I posted was "first light" imaging with the 8" LX200, I have had others (12" Classic and a 10" GPS) but gave up on the hobby mainly due to time and stuff like this.
I think in many cases some people who do this have forgotten what not knowing is like and or had someone get them past certain things... It sure seems like max imaging time with Alt/Az should really be 1 second, maybe 3 not the 30 so often told of all over and the reason I say this is there is usually follow up to such questions which indicate 330 seconds is more like a maximum anomaly and not close to a norm one should expect...
In my case I have the ultra wedge and want to use that when I drag this scope to dark skies at my cabin in northern WI...but down here by Milwaukee it's not worth a pier nor a ton of effort due to light pollution so I was hoping there was some quicker and easier ways with Alt/Az because I would probably be happy with 8 to 12 second exposures compared to what I get now...
Posted 07 April 2013 - 09:50 PM
Posted 07 April 2013 - 11:12 PM
The more I think on this the more I think I should just get a GEM and perhaps a small refractor like say an 80MM ED and try that for imaging from home and maybe just use the LX200 for visual and or leave it up north where I could build a more permanent spot for it that would be worth it, at home the light pollution is bad enough to where investing in a more permanent spot given my yard is not worth it, as it is I can only do things to the east exclusively due to trees and other obstructions.
This thought hold more value as well because I usually like to image Jupiter or Saturn then switch to messier objects and my scope can be collimated fine, but then adding a 6.3 reducer for deep space throws that off and I am not sure how to deal with that, I don't want to re-collimate several times an evening... but I wonder how others handle this problem... hmmm think I will post that as a new topic...
Posted 07 April 2013 - 11:31 PM
Posted 08 April 2013 - 12:05 AM
I might invest in a GEM though... everytime I get into this hobby I wind up getting and LX200 because it just seems like it should be easy and then I hit a brick wall all everytime...
Posted 08 April 2013 - 02:59 AM
The photograph alt/az mode is possible and can be done in two ways:
1) with tracking without derotator field with maximum limit which varies from 15 to 120 seconds depending on the height of the photographed object.
2) derotator field with long exposure. This means that you can get individual shots, even an hour each.
To get good results you have to "tame" the instrument. LX200 is a great telescope, but not for everyone because it is an object that in AP is not an "out of box" ready to go, but we need to "fine-tune". I saw your picture and I think I know what is your problem. Now I do not have time, but I will explain the best steps you should do to get a good tracking exposure to 30 seconds (if that's what you care).
In this session I recently posted a picture of M82 (now should be to page 2). Try to look at it. Was made in Altazimuth mode with my LX200R 12" and is a combination of many frames ranging from 5 to 40 minutes each. However, to obtain this result it takes some accessories because a LX200 "standard" will never give this result.
Posted 10 April 2013 - 05:46 PM
My first move was to pick up a better imager (I had 3 Meade DSI's - OSC v1, OCS II and a v1 Pro )... So I picked up an SBIG ST-7 XME, that is my first move... I am now looking for a filter wheel to match it... I will be selling at least 2 of the DSIs, might keep the pro1 to guide with and or the II OSC just to have a color option, thinking on that...
Once I get a filter wheel I think I am going to pick up a CG5 and an 80MM ED to learn a GEM in the meantime I will play with the wedge...
It's the best plan I can think of I can afford.
Posted 10 April 2013 - 06:00 PM
With the wedge I think you will be quite satisfied for the next stretch. You may find you will not really need to rush to get a CG5/80mm ED.
I have been very happy with my superwedge on the 10" LX200 for the past 21 years...
Posted 10 April 2013 - 06:16 PM
Posted 11 April 2013 - 04:53 PM
Posted 19 April 2013 - 06:16 PM