Page 1 of 1
Meade LX200 Microfocuser
Posted: Tue Apr 13, 2021 8:26 pm
by sdbodin
I have been chasing a bit of an alignment error for some time and found the culprit. The microfocuser was miss-aligned by a couple degrees!! I think this amendment to the LX200 manual page 14 should be printed by all and pasted in!
A bit harsh, but appropriate considering the time I have spent and fully believing the warning label.
Steve
Re: Meade LX200 Microfocuser
Posted: Sun Oct 03, 2021 2:24 pm
by Star Dad
I'm going post this message here because I am having an issue with focusing my club's Mak. The situation is: I can obtain a pretty decent focus using a 40 or 30mm lens. (FL is 2670 I believe). But I put a 9mm in and it is horribly fuzzy. I cannot get pinpoint stars - they are blurry - and you cannot really make out the bands of clouds on Jupiter. Now a 9mm should give about a 296X magnification. It's a 7" MAK - which theoretically should max out at 350X. Given that all the hype I have read indicates that Maksutov-Cassegrains are superb for planetary - am I expecting too much from this scope / magnification or do I have an alignment problem. I did do a visual - "look down the tube" and it seems to show concentric rings - but I am not positive. I have NOT done a star test yet... been out in the field these past two clear nights doing outreach programs. I will do it as soon as I can - which looks to be at least a couple of days from now. Comparing views with my 8" Newt - I find the Newt gives a superior image using similar magnifications in both scopes. The focuser on the MAK seems a little "mushy" . That is it takes a bit of rotation until the focuser "kicks in" /"grabs". And it happens in both directions. Just for some background - I presume this scope was donated - so maybe it is out of alignment? But as I said above, given the hype (and expense of this scope) I would expect superior views from it and I just am not seeing it. Any advice or comments?
Re: Meade LX200 Microfocuser
Posted: Sun Oct 03, 2021 3:39 pm
by notFritzArgelander
Star Dad wrote: ↑Sun Oct 03, 2021 2:24 pm
I'm going post this message here because I am having an issue with focusing my club's Mak. The situation is: I can obtain a pretty decent focus using a 40 or 30mm lens. (FL is 2670 I believe). But I put a 9mm in and it is horribly fuzzy. I cannot get pinpoint stars - they are blurry - and you cannot really make out the bands of clouds on Jupiter. Now a 9mm should give about a 296X magnification. It's a 7" MAK - which theoretically should max out at 350X. Given that all the hype I have read indicates that Maksutov-Cassegrains are superb for planetary - am I expecting too much from this scope / magnification or do I have an alignment problem. I did do a visual - "look down the tube" and it seems to show concentric rings - but I am not positive. I have NOT done a star test yet... been out in the field these past two clear nights doing outreach programs. I will do it as soon as I can - which looks to be at least a couple of days from now. Comparing views with my 8" Newt - I find the Newt gives a superior image using similar magnifications in both scopes. The focuser on the MAK seems a little "mushy" . That is it takes a bit of rotation until the focuser "kicks in" /"grabs". And it happens in both directions. Just for some background - I presume this scope was donated - so maybe it is out of alignment? But as I said above, given the hype (and expense of this scope) I would expect superior views from it and I just am not seeing it. Any advice or comments?
There might be an alignment problem but it could also be a thermal issue, large Maks need to cool down to be at their best. Did you try your 8" Newt and the Mak side by side on the same night? If not, it could be atmospheric seeing related. Maximum magnification only works well under perfect skies. If you did compare on the same night, then it's likely the Mak has alignment or thermal issues.
On my 6" Mak it often takes upwards of a half hour for the stars to become points unless I cold soak prior to setup.
Re: Meade LX200 Microfocuser
Posted: Mon Oct 04, 2021 5:57 pm
by Star Dad
Yes, both scopes were side-by-side. They both had 2 hours of cool down time - not that there was much to cool down - I keep them both in my outside garage... no heat. According to metoblue seeing was supposed to 5 out of 5.... a very rare occurence in my neck of the woods. Which is why I tested this out. On the flip side, though, we were at a dam and the ground was pretty wet - not soaking, but I'm sure there was a fair bit of humidity in the air. I realized yesterday evening, while searching for a 15mm eyepiece to buy, that I have a decent zoom lens. So I'm going to try it out and see where the fuzziness starts. As I said above, I will do a star test later this week after the rain and clouds have passed on and I get a semi-clear night.
Would a Mak be subject to collimation errors brought on by jostling of the vehicle in transit? I know my Newt suffers from that, especially rough roads.
Re: Meade LX200 Microfocuser
Posted: Mon Oct 04, 2021 8:57 pm
by notFritzArgelander
It’s definitely out of collimating then or you’ve got a bad example. My MK66 has only required collimation twice in nearly 20 years. Both times after crossing the continent on moving. I’m a little surprised that your Gregory Mak would be more sensitive than my Rutten Mak, so that worries me that maybe it was never quite right. I’m hoping that your star test and collimating efforts cure it. I’m jealous of nighttime good seeing so I use a laser during daytime.
Re: Meade LX200 Microfocuser
Posted: Thu Oct 07, 2021 11:24 pm
by Star Dad
I just did a star test on Polaris. The verdict? low power (40mm) showed a perfect donut. High power (9mm) showed a perfect donut. However, at 9MM (~300x) the star was not a pinpoint - more like a fuzzy dot with 3 "spikes" radiating from it. As I was going out of focus I saw a pentagon, the a hexagon, and octagon and then a circle. Not sure what this might mean - other than I am pushing the theoretical 350x limit, which I have read (somewhere) that for this scope 300X is the max magnification. So I am hoping someone will say that I am right and I'm just expecting too much. And dang, I just remembered I wanted to test it with my zoom lens. Well that will just have to wait as I see solid clouds for the next 7 days in the forecast. And tonight the clouds are rolling in early - not worth setting up for AP. This of course is New Moon time which = clouds.
Re: Meade LX200 Microfocuser
Posted: Fri Oct 08, 2021 12:54 am
by notFritzArgelander
Star Dad wrote: ↑Thu Oct 07, 2021 11:24 pm
I just did a star test on Polaris. The verdict? low power (40mm) showed a perfect donut. High power (9mm) showed a perfect donut. However, at 9MM (~300x) the star was not a pinpoint - more like a fuzzy dot with 3 "spikes" radiating from it. As I was going out of focus I saw a pentagon, the a hexagon, and octagon and then a circle. Not sure what this might mean - other than I am pushing the theoretical 350x limit, which I have read (somewhere) that for this scope 300X is the max magnification. So I am hoping someone will say that I am right and I'm just expecting too much. And dang, I just remembered I wanted to test it with my zoom lens. Well that will just have to wait as I see solid clouds for the next 7 days in the forecast. And tonight the clouds are rolling in early - not worth setting up for AP. This of course is New Moon time which = clouds.
My experience with my MK66 Mak is that n-gons indicate that thermal equilibrium has not been reached, however the n is always = 3. This is because the separate secondary mounted on the corrector plate has 3 screws for collimation and the thermal stress of cooling creates a triangular stress pattern in the secondary. If you were sure you were in thermal equilibrium, I'd guess that the optics on the primary and/or corrector are getting pinched somehow.
IMHO you are not expecting too much.
Re: Meade LX200 Microfocuser
Posted: Sun Oct 10, 2021 3:42 pm
by Star Dad
I have a chance (maybe) this coming Friday to repeat the experiment... I am not sure the scope was in thermal equilibrium. I was in a hurry trying to get a star before the clouds rolled in. The scope was in the Van - outside but fully shaded from the sun for a couple of hours. The interior did not feel warm as opposed to the external air temp... but there was no "cool" down period. Hopefully the weather gods will adhere to predictions and Friday night will be clear... when I should easily have time to achieve thermal equilibrium. There is hope yet. Thanks notFritz!
Re: Meade LX200 Microfocuser
Posted: Sat Oct 23, 2021 4:07 pm
by John Baars
Star Dad wrote: ↑Thu Oct 07, 2021 11:24 pm
I just did a star test on Polaris. The verdict? low power (40mm) showed a perfect donut. High power (9mm) showed a perfect donut. However, at 9MM (~300x) the star was not a pinpoint - more like a fuzzy dot with 3 "spikes" radiating from it. As I was going out of focus I saw a pentagon, the a hexagon, and octagon and then a circle. Not sure what this might mean - other than I am pushing the theoretical 350x limit, which I have read (somewhere) that for this scope 300X is the max magnification. So I am hoping someone will say that I am right and I'm just expecting too much. And dang, I just remembered I wanted to test it with my zoom lens. Well that will just have to wait as I see solid clouds for the next 7 days in the forecast. And tonight the clouds are rolling in early - not worth setting up for AP. This of course is New Moon time which = clouds.
You are not expecting too much. I have seen this pattern before. In my case it was pinching...