Coronado 90mm. I can only see part of the sun with details

[vicmanpc]

Good day, I have the Coronado Solarmax II 90mm DS 30mm BF telescope. Using the double stack I can only see details in about 25% of the eyepiece (possibly using a single stack or etalon is the same). It is necessary to move the telescope, the Tmax tilt wheel or the tuning ring to be able to see the details of another 25% of the sun, but I can no longer see other details of the rest of the sun. I've already tried all kinds of configurations with no success. Do you know any solution for it, or maybe the etalon or some part of the telescope is faulty? Thank you and excuse my bad english

[marktownley]

Hi there, welcome to the forum. Sounds to me like it is off band. How long have you had the scope?

[vicmanpc]

Thanks marktownley. Almost 3 years, I suspect It has always had the same problem. I also have a Lunt 60mm with Pressure Tuner / B1200 / Crayford Focuser with Double Stack LS60FHa that I use more by the portable, and the latter has a similar problem that I just detected, but the sharpness is 50% to 75% of the eyepiece, using the Baader Hyperion Mark IV eyepiece in 24mm (I have 2 identical eyepieces and it is the same problem.) But moving the telescope a little, the other part of the sun is sharp with details, and the rest is the orange circle of the sun without details. Perhaps it is a common problem of all solar telescopes

[EGRAY_OBSERVATORY]

If you are able to use some-sort of camera (say a mobile-phone type) as aforfocal through the eyepiece or even straight through the B1200 and post your image(s) here, it would help us to resolve your problem.

Cheers
Terry

[Montana]

A very warm and sunny welcome

It is difficult to say whether it is faulty or not. A hydrogen alpha scope is always on band only in a small region (although pressure tuned should be more even across the field). With my Solarscope I would say it is about 75% of the whole field of view in my particular eyepiece (that I use) and I have to move it around to see best features on one side of the Sun then the other.

The best person to ask is James (Deepsolar) as he has a Coronado 90mm and is very good eyeball observer and would be able to say what he sees, this would help you gauge whether this is 'normal'

Alexandra

[DeepSolar64]

I rarely see a uniform tuned view through either of my Coronado scopes, if ever. There is always a sweet spot. In my 90 it seems to usually be right of center in the field. It’s something that takes getting used to. Adjusting all three tuners on my DS scopes can minimize it. It takes a little work sometimes. And for some weird reason it sometimes shows detail really well at some point at the edge of the field.

I have never looked through a Lunt to compare them. One thing for sure. It’s never as uniform as a white light image!

Persistence pays off. The scopes will show the details once you learn how to use them.

In the 90 I can often exceed 50 percent of the field in tune. In the 60 it is usually less. I don’t know why. I think the tilt-tuned systems have their idiosyncrasies.

James

[vicmanpc]

Thank you for your valuable comments. I think I will get used to that detail, hopefully Lunt and Meade specify that, in their advertising before to buy, so that customers do not believe that it is a defect, and each one who buys it knowing even what they will be able to see. Cheers
Victor

[DeepSolar64]

When I first bought my Coronado Solarmax II 60 I had trouble seeing anything in it at all. I could see only the brighter prominences. Like you I quickly found out that the scope did not show everything evenly tuned throughout the field and the field also can be unevenly illuminated. Learning to adjust the tuners helps a lot and even then you still have a sweet spot that you have to move around the field a bit to see the best detail. But you get used to that after awhile. I also had to learn to see in the red light of hydrogen-alpha. Your eye is far more sensitive to yellow and green wavelengths than red. I have also found out that often when I first look into the scope to let my eyes adjust. Ha, especially in double stack can be quite dim and the eye is not that sensitive to that red light anyway. Wearing a wide-brimmed hat helps shield direct sunlight out of my eyes while I observe. Often the longer you look the more you can see. I use current GONG images to guide me and even recent images from SolarChat members can be of a big help, Rainer and Pedro Re come quickly to mind here. Your SMII90 is a nice instrument and can show considerable detail. It certainly excels on limb detail. Proms and spicule layer. Single stack gives a brighter image allowing higher magnifications too, given decent seeing.

I liked my 60 so well I bought a 90! But I must confess I was originally looking for a Lunt LS100Tha pressure tuned scope. Lunt had switched to the modular line and I caught a double-stacked Coronado SolarMax II 90 on sale for 3499.00 which was half the cost of the Lunt MS100. The Lunt might tune a little more evenly but the cost made it possible for me. I certainly don't regret it!

Enjoy!

James

P.S. I dream of a Lunt LS152Tha double-stacked scope and a tracking mount to hold it and an observatory to put it in. Hey, dream big I say!

[marktownley]

How is disk evenness in single stack mode?

[yltansg]

Hi Victor,

I agree with Mark to start with the view using a single etalon. Get that right and then add the second etalon.

ALFRED

[Highbury Mark]

I’ve owned two double stacked Lunts and currently have a pair of 70mm Solarscope filters that I use with a separate refractor, and they have all had uneven detail across the fov, but typically they display 50%-75% of the fov on band. One way to adjust the sweet spot (apart obviously from tuning the filters) is to slightly unthread the outermost filter - a technique known as clocking. Don’t know how easy that is with Coronado scopes? Changing blocking filters can also make a difference. If you have the chance to test another Coronado blocker it would be interesting to see the result.

[DeepSolar64]

HM,
I have never really thought about that with my Coronados. They have a tuning ring at the very front of the etalon in addition to the tilt wheel. It seems to work well. I'll remember this suggestion though.

Does any of the Lunt scopes or the Solarscope tilt-tuned models have a front tuning ring in addition to the tilt tuning wheel or is it proprietary to Meade Coronado?

James

[Highbury Mark]

No, they don’t James.So maybe my clocking suggestion isn’t relevant for Coronado owners?

[DeepSolar64]

The internal etalon has only a tuning peg which serves the same purpose as the tuning wheel. It lacks the additional tuning ring.

[vicmanpc]

How is disk evenness in single stack mode?

Thanks for the suggestion marktownley and yltansg. In fact, the sun in single stack mode looks uniform and complete, but with its shortcomings, in the Coronado 90mm. The problem arises when placing the second Etalon. I also tried all the possible holes of the RichView tuning lever for internal Etalon.The strange thing is that in the Lunt 60mm it also has the same problem in single stack mode and with the double Etalon. I wonder if it would have the same problem when using a MALLINCAM SKYRAIDER DS2.3 PLUS camera to take video without processing, the same one that NASA used for the 2017 eclipse that I have not used yet due to lack of time. Here many also mention that this detail is common, although in my opinion it is not normal or acceptable for such an expensive product: https://www.cloudynights.com/topic/6624 ... a-lunt-60/

Victor

[marktownley]

it is not normal or acceptable for such an expensive product

Hi Victor,
It's not normal, neither is it acceptable, sadly it is all too common (poor performance) from solar manufacturers in general

Based on what you've said so far and how much you've persevered with getting the double stack right I would say that particular unit is just not suited to your scope.

Mark