21 replies to this topic

[McDoggin]

After having spent many nights with repeated alignment failures on my LT 8 ACF I have discovered that it is usually due to the fact that I do not have the base of the single fork arm PERFECTLY level. In addition to the eyepiece bubble level / compass that came with the telescope I use three additional levels to make sure everything is absolutely level prior to running the alignment routine. Once I think everything is perfectly level I also usually then drive the telescope around to make sure everything is still level when the weight distribution of the OTA relative to the base is changing. My guess is that I spend at least 45mins just leveling the telescope. But, when I do this I typically get the message indicating that alignment has succeeded the first time I try. I am starting this thread to discuss the algorithms or procedures to get the base level because I feel that 45mins (or longer) is far too long to spend setting up the telescope. My leveling procedure goes something like this: 1) Find relatively level spot with a good view. 2) Place the telescope already mounted on the tripod onto the selected spot. 3) I wiggle the tripod legs a bit and then make sure the end nut securing the telescope to the tripod is hand tight. 4) I place the eyepiece compass/bubble level into the diagonal prism. 5) I place a level across the face of the eyepiece bubble level and adjust the angle of the diagonal prism. 6) I place a two-axis level on top of the speaker grill on the base of the single fork arm. 7) I orient the two axis level toward one leg call it "leg A" then I adjust leg A so that both levels are close. 8) Then I shift the orientation of the two-axis level to point at the next leg "leg B" and adjust leg B so that it reads basically level on both axes. 9) I repeat this again with leg C. 10) Now the really time consuming part: repeat steps 7 - 9 making incremental adjustments until the two-axis level shows level in every possible angle of rotation. 11) Slew the telescope AZ to make sure the levels are centered with the OTA in several different directions, if not then repeat steps 7 - 9. 12) Level the OTA using the eyepiece bubble level and a level at the rear of the OTA. 13) Run the alignment routine. I am not claiming that this procedure is optimal in any way but it does work. I am sharing my procedure so that I can learn from others and hopefully shave some time off of my setup. I am interested to hear from others the amount of time they spend in setup and the procedure being used to level the scope and the relative success rate. Based on other topics it sounds like using the magnetic north alignment may be buggy and confounding the alignment problems I have. The next time I go out I will try using the true north method with the base leveled out fairly good and report back.

[Matroskin]

Interesting experience. To tell the truth, I never use such a complex and long procedure to level my LT-8 SC. 2-3 minutes for levelling and 2-5 minutes for alignment. BTW I never place a bubble level/compass into the diagonal and to tell the truth I seldom use this bubble level/compass at all. As a compass it is useless, as a level it is incomfortable...

[McDoggin]

Thanks for the reply! I am now more hopeful that I will be able to significantly reduce the setup time. Two questions about your procedure 1) If you do not use the bubble level/compass that fits in the eyepiece how do you level the OTA? I have been placing a level along the ridge of the bracket attached to the OTA that connects it to the single fork arm. I have observed that if the rear of the OTA is level then the front is not. So I have also been placing a level across the face of the eyepiece bubble level to double check that the OTA is level at the end of the diagonal prism (it usually is) . Since the OTA itself does not seem to be level I assume that the computer's reference for level is when the end of the diagonal prism is level. 2) What are you doing to make sure the base is level? I am thinking of buying a "bull's eye" level for the base. I agree the compass is useless. Thanks for your input.

[gunfighter48]

Go to a good hardware store and buy a 2 way plastic mounted level. Buy some double sided foam mounting tape and stick it to the right side of the base, to the right of where the handset rests. I did this on my LS8 and leveling takes 2 or 3 minutes.

http://www.lowes.com...ge=2&facetInfo=

[Matroskin]

As for me, I use a "Bubble Level" application of my telephone - sure it is not 99.99 precious, but it is enough to level a telescope. I just place a telephone on the tube/base and watch. In fact if a bubble level/compass had some light inside it would be much more useful... And BTW a telephone has a GPS application to supply me coordinates.

[McDoggin]

Go to a good hardware store and buy a 2 way plastic mounted level. Buy some double sided foam mounting tape and stick it to the right side of the base, to the right of where the handset rests. I did this on my LS8 and leveling takes 2 or 3 minutes.

http://www.lowes.com...ge=2&facetInfo=

So the link you posted is exactly the two-axis level I am currently using. It looked to me that the head of the tripod is approximately under the speaker grill so thats where I place it to measure level. I got a slightly different answer about level if I placed the level to the right of the handset which I agree is the natural place to put it. I just bought this level : http://www.amazon.co...0?ie=UTF8&psc=1. I think this may work better so that I can see precisely which angle I am off in and then adjust those legs. I would also prefer not to have to rotate the level to check other orientations. Are you using the true north or magnetic north alignment routine? It sounds like in general people are spending a few minutes leveling the base and as long as it is relatively close to being level there are no major problems. The only other question I have for you is: don't the LS models level themselves? BTW I also downloaded a bubble level app for my iPhone and I will check that out and report back.

[Matroskin]

In fact, I cannot understand why to try to get perfect levelling - each level of precision has it's own costs... including time costs. When I set my LT-8 onto the snow, sand or soft ground, the surface will always slowly "wrinckle" under a telescope's weight, so all your attempts to level a tripod/mound perfectly will be in vain. Plus/minus one degree is in my opinion enough precision for LT alt-azimouth... Ah, yes, I never use magnetic north alignment - only true north.

[McDoggin]

In fact, I cannot understand why to try to get perfect levelling - each level of precision has it's own costs... including time costs. When I set my LT-8 onto the snow, sand or soft ground, the surface will always slowly "wrinckle" under a telescope's weight, so all your attempts to level a tripod/mound perfectly will be in vain. Plus/minus one degree is in my opinion enough precision for LT alt-azimouth... Ah, yes, I never use magnetic north alignment - only true north.

Yeah I agree. Its just if I don't get the base level I fail alignment. On the next clear night I will only spend 5 minutes aligning the base and get it within one degree and then use the true north method. I strongly suspect that the true root cause of the alignment failures is using magnetic north. I will report back once I verify it. Thanks so much for your input.

[gunfighter48]

The only other question I have for you is: don't the LS models level themselves? BTW I also downloaded a bubble level app for my iPhone and I will check that out and report back.

I have watched my LS8 and I can't see that it physically levels itself. I think it's more a case of feeding corrections into the alt & az settings so that it appears to be level. I get a reasonalbly close level and then let it do its alignment and it does just fine each time. The only time it's failed is when there was too much twilight, the sky was too bright. If you don't get a fairly good level your goto will be off and things won't line up correctly in your eyepiece.

[McDoggin]

We had a clear night tonight in Austin and I had the opportunity to try out the iPhone bubble level and the true north alignment routine. It took me approximately 5mins to level the scope: I was off by ~0.3 degrees in the x-axis and ~ 0.2 degrees in the y-axis. I am happy to report that alignment succeeded on my first attempt (Arcturus and Altair). Thanks so much for the help -- it was nice to finally be able to observe without all of the frustration of repeated alignment failures! M13 is AWESOME! To be complete I will keep a record of the success rate using this alignment technique... but its 1/1 so far.

[Matroskin]

Really good to hear that a good piece of gear works good! *Thumbs_Up* Congratulations!

[McDoggin]

Last night I spent five minutes leveling the scope this time with both the iPhone level app and a real bulls-eye bubble level. Both were in agreement and I easily had the bubble within the target, I was off less than 0.3 degrees in all directions. Again I used the true north alignment routine with "Easy" alignment choosing Vega and Altair. The telescope was able to successfully align on the first attempt, so I am 2/2 using this method. Previously I exclusively used magnetic north and had problems achieving alignment 99% of the time unless the scope was perfectly level. I highly recommend using the bulls-eye style bubble level. I think it is much easier to use than the two axis level because it gives you so much more information. The iPhone app I am using is called "Clinometer" its a beautiful app that works well but it was a little pricey (IMO). Next time I go out I will level the scope the same way and try both magnetic north and true north alignment routines.

[Matroskin]

Oh, glad to hear! Keep up! Here's the awful weather so I can only envy your observations. Just yesterday I purchased a new UHC filter and due to those ugly clouds I cannot test it... BTW I use Android-based mobile and my Bubble Level application was free.

[McDoggin]

I have been out twice more since the last post. I am 4/4 using the 5 minute true north + bull's eye bubble level alignment procedure. I also repeated the magnetic north alignment after I leveled the scope with the bull's eye level and this succeeded on the first attempt as well! For the record I am going to estimate that my success rate for magnetic north alignment so far is 5/30. After reflecting on this I think it just comes down to the sum of errors. There is error in the time and location entered into the handset, error in the level of the base and OTA, and error in the direction the scope is pointing. If the sum of these errors is greater than some threshold then alignment can not succeed. I believe (based on limited data) that the true north alignment is inherently more accurate than the magnetic north alignment. There may be local magnetic fields that affect the compass or like Matroskin pointed out there may be errors in the calculated RA/DEC when the computer is trying to compensate for magnetic north alignment. My experience with having to get a perfect level probably reflects the total error of all the other variables; so there was no margin left for error in the level of the base. Therefore I believe that the time and location entered into the handset should be as accurate as possible, then there should be more margin for error in the direction and level of the scope during alignment. To this end I purchased the "Star GPS" NX02 and tried it out last night. For the first time ever the telescope came super close to the alignment stars and I only had to make fine corrections to center the stars in the eyepiece. I think this reflects the error that I previously had in time and location (location is likely the biggest factor). I recommend Star GPS but I don't think it is critical since you can look up the time and coordinates of your viewing location and enter them into the telescope manually. Previously I had just used my ZIP code for the site location.

[Matroskin]

On the surface of the Earth each distance means some angle, and each angle means some distance. For example, 60 miles equals 1 degree, and 1 angle minute means 1 mile. If you use a standard 26 mm eyepiece on the LT-8, you have a field of view that equals ~ half a degree, or 30 angle minutes. So I think to use a ZIP code or a name of the closest big city is not good. Each time when I ride somewhere w/my telescope I check Google Earth or real (paper-printed) maps and set the exact coordinates. Autostar doesnt take seconds ("), only minutes - so the error must be not more than +/- 1 mile.

Several times I used a compass to set up my telescope, but not via "Magnetic North" on the Autostar remote. I took a normal compass, a table of magnetic deviation (~ 10 degrees to East for my area), and set up a north point taking 10 degrees left from the point a compass needle points to. It is very useful for searching planets just after the sunset, especially Mercury.

[McDoggin]

That is great information! I never even thought to manually correct for the error in magnetic north. For what its worth here is a link to a map of magnetic variation around the world: http://msi.nga.mil/M...es/mv-world.jpg . The information appears to be accurate for my location.

[McDoggin]

Matroskin when you get a chance you should post something about your UHC filter. I am curious to find out how much of a difference it makes. My typical viewing location is fairly light polluted and I have been contemplating buying a filter and I would be interested to learn from your experience.

[Matroskin]

A great map, thanks! I always used noaa.gov service for taking a magnetic declination, but these days all NASA services (like APOD, SkyCal, NOAA etc) are offline due to those stupid financial problems. And yes, I am eager to test a UHC filter - but there's still cloudy ((. Here where I live skies can be cloudy since September to January - usually there's some clear "window" in the beginning of October for a week or two long, but not this year. ((

[MistrBadgr]

And I thought I had a bad cloud situation sometimes! I need to be thankful for the weather I have.

Bill Steen

[Matroskin]

Hurray! This night was clean and I worked with the telescope on my balcony testing UHC filter. You know, I like the effect. The light pollution level here is rather high (city's size is near a million citizens). Usually in my LT 8 SC, when I watch from the balcony, M42 (Great Orion Nebula) looks like triangle with a dark hollow on one side. But with the UHC filter I instantly saw "wings" (or as somebody calls this detail "a moustache") spreading from the center triangle. Sure the image was not as astonishing as in the real dark place far from the light pollution, but it was a good compromise in my opinion. PS Alignment procedure - 1-star (Betelgeuse), quick and precise. Watched М35, М67, М44, NGC2169, Juppiter, Mars. Tried to find the comet (ISON C/2012) but failed. I suppose it's still too faint for viewing from the city.

P.S. http://astrodummies....3/2013-10-15-31