Today's SUN (20171027) | Coronado SM90II problems

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pedro
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Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Today's SUN (20171027) | Coronado SM90II problems

WEBLINK:
http://re.apaaweb.com/sun_h_alpha_2017-10.html

My Coronado SM90II was recently serviced by Meade but I'm still getting low contrast images with the TV101. Any ideas?

Can it be a focal ratio issue, the TV101 is F/5.4. Should I use it with a larger focal ratio (F/10)?

Image
IMAGING SETUPS

Image
IMAGING SETUPS

Image
SUN (20171027) H-alpha DISK & PROMS (11:00 UTC). TV101 F/5.4, SM90II, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M

Image
SUN (20171027) H-alpha DISK & PROMS (11:00 UTC). LUNT60, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M

Image
SUN (20171027) H-alpha DISK & PROMS (11:00 UTC). TV101 F/5.4, SM60, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M

Image
SUN (20171027) H-alpha DISK & PROMS (11:00 UTC). TV101 F/5.4, SM60, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M

Image
SUN (20171027) CaK PROMS (11:00 UTC). TV101 F/5.4, LUNT 1200 CaK Module, PGR GRASSHOPPER 3 GS3-U3-28S4M

Image
SUN (20171027) WL, CaK & H-alpha (11:00 UTC). TV101 F/5.4, LUNT 1200 CaK Module, SM60, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M
Last edited by pedro on Fri Oct 27, 2017 7:06 pm, edited 1 time in total.


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Re: Today's SUN (20171027) | Coronado SM90II

Post by pedro »

Coronado SM90II
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Re: Today's SUN (20171027) | Coronado SM90II

Post by marktownley »

It's just off band for your local conditions (sadly) Pedro. F-ratio isn't going to do much I think. The shots are off band; if they were on-band but lacking in contrast a longer focal ratio may help the blocker with less continuum leakage. Would be interested to see a shot taken with it before Meade has fiddled with it. Short of totally replacing the plate spacers, which I seriously doubt they have done, I don't see how they could do anything to it to improve it on what it was originally. I think that all that has happened is that somebody has wiped it with a cloth :(

You do have a nice collection of images though, and the other Ha shots do show what the on band disks should look like.


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Re: Today's SUN (20171027) | Coronado SM90II

Post by pedro »

Thanks for the comments Mark

Before it was worse or maybe not. Check out these images (before servicing)

Image
SUN (20170205) H-alpha DISK & PROMS (10:30 UTC). TV101 F/5.4, SM90II, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M

Image
SUN (20170216) H-alpha DISK & PROMS (10:00 UTC). TV101 F/5.4, SM90II, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M

Image
SUN (20170216) H-alpha DISK & PROMS (10:00 UTC). TV101 F/5.4, SM90II, BF30, PGR GRASSHOPPER 3 GS3-U3-28S4M

What do you think?

I get much better results with my other etalons from Meade (old and new)


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by marktownley »

Hmmmm. I don't see no difference in the before and afters. Will it work better as a double stack maybe?


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Thanks again Mark

It's a good suggestion. I will have to try it


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by Derek Klepp »

Good luck Pedro.These Ha etalons are very temperamental.


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by Montana »

Lovely shots Pedro but yes, the SM90 is off band, that is bad luck, hopefully it will work better in double stack ;)
:hamster: :bow
Alexandra


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Thanks guys

I tried it again today and definitively it's off band

It was serviced in the Mexico Meade factory (150 US$ repair service)

As Mark mentioned I guess they only dusted the etalon

Now I have a big paper weight...

Visually in not as bad though


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by marktownley »

They're just very sensitive to local conditions. I bought Walters SM90ii etalon off him 3 or 4 years ago, in Wolfhalden at >700m altitude it worked great, however when it ended up in Brierley Hills (~100m altitude) it was way off band and nothing I could do would bring it on band. Maybe these Mexican etalons work great in Mexico City (2500m altitude) but then are out of spec for us folk closer to sea level? Perhaps this is why the Isle of Man Coronado etalons are 'better' as they are better suited to more sea level environments?


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by Valery »

Hi Pedro,

F/5.4 is too fast for the blocking filter! Lunt suggested to have at least F/7 for blocking filters.

My experiments showed me that contrast improves with F/D decreasing up to about F/12.
Also, with temperature drop the blocking filter's bandpass shits more to the blue.
So, even more important to have a slower F/D at the entrance of the BF.

Any tilt in the focuser will also shift the BF bandpass boundaries to the blue.

Hope this helps.


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Thanks Valery & Mark

I use my TV101 (F/5.4) for most of my FD imaging. I tested all my Coronado Etalons today and the results are very interesting (I will post the images later on today)

Using the same OTA the contrast and details on the chromosphere vary a lot. The SMIIs (Meade) are significantly worse than the pre-Meade etalons (at least the ones I have)

I will have to try the SM90II with a longer Focal Ratio but I suspect that I will get low contrast images. The Pre-Meade SM90 I had was great at F/5.4 (TV101)
Last edited by pedro on Mon Oct 30, 2017 10:07 am, edited 1 time in total.


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by Valery »

Pedro,

I too have had a pre-Meade SM90 etalon. It was VERY contrasty. The most contrast air spaced etalon I have ever seen.
Countless times I have regretted about my crazy decision to sell it.

OK, back to your problem. Try to use at least 1.5" Barlow prior to the BF.

If you have another etalon, then this low contrast etalon is a best choice for DS. With wider etalon your DS will have the largest sweet spot.
With narrower etalon - the smallest sweet spot. So, you do not loose! This is a best ace for the DS!


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Thanks Valery. I will try do it, using the SM90II for DS

I also regret selling my pre-Meade SM90.


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Thanks Mark

You might be right. Using a SM90 at 2500m or at sea level is not the same thing. They should now better, or maybe not...

best regards


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by marktownley »

Any news Pedro?


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Yes Mark

They want me to return the etalon to be repaired free of charge. The only problem is that I have to do a temporary export and that will cost at least 500 US$... Not sure what to do


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by eroel »

Pedro:

The Mexican Meade factory is situated at almost sea level, (near San Diego but on the Mexican side) so the altitude is no problem.

BTW, I have a Solarmax 90 and when I got it home it did not perform well because it was out of band, so what I did to get it in tune was to mark where the pin is, then took the pin out and while looking at the sun I slowly screwed the pressure tuner out a few holes and tested, then got to the original pin place and checked again and then screwed in a few more holes (from the place where the pin originally was) until I got more contrast, when happy I placed the pin at the middle of the turning sector and tried again moving the etalon at every posible place permitted by the pin.
I was careful not to get too much pressure on the etalon by screwing it to much, just a couple of holes more.
I also moved a bit more the tilting hinge, so that it moved the same amount up and down, and when at the center, the gap all around the two etalon parts held by the hinge were perfectly parallel, for that I used a feeler gauge and an Allen wrench so to place the 2 parts parallel, this also helped a lot to get more contrast and less hotspots.

The BF´s are also very important, so I tried the ones I have (BF10, BF15, BF30), being the BF15 the one that gives a more contrasty view, though I did install the BF30 because it gives a more even field.

I remember David Lunt, Bill Dean and myself, testing many 40mm Coronado etalons, so to match a pair for using at my home observatory that is at 2250 meters above mean sea level, we did the pairing at the Riverside Telescope Making Convention many years ago, we even paired the BF10 among many that he had, so the pairing was done at high altitude, the RTMC was held in a place near 7000 feet above sea level.
I still keep this paired etalons and are really good for its size, I have them mounted on a 76mm f/6.4 TeleVue refractor.

Pedro, this was my experience and did it at my own risk, but it worked nicely.

Abrazo,

Eric.


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by MapleRidge »

Hi Pedro...

I am at a loss to make any suggestions, but a relatively easy test would be to use a barlow with the scope, or test it on a scope that is F10 or so just to eliminate the focal ratio being the culprit.

Good luck finding a fix!

Brian


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Re: Today's SUN (20171027) | Coronado SM90II problems

Post by pedro »

Thanks Eric and Brian

Eric: I already removed the pin and tried it with the pressure tuner in several positions. It seems that this is not the issue

I still have to try other BF (tried only the BF30). I also suggested that another repaired etalon (SM90II) could be sent to me and I would return the one I have. I'm still waiting for an answer.

Thanks for your comments


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