Sun 12-07-14 what's causing problem ?

[Davey-T]

Took this in not very good conditions using LS60 DS but it seems to be over exposed to one edge and under exposed on the opposite edge.

Is this because it's not tuned correctly or because the chip is at an angle or some other reason ?

Dave

[FunkyKoval35]

Yes, it is possible that chip is on some angle. Can you show us a master flat?

[Davey-T]

Only just started Solar imaging so haven't delved into flats yet, if I rotate the camera will the over exposed / under exposed bits swap sides if the chip isn't square ?

Dave

[SimonfromSussex]

You probably need to rotate the second etalon Dave.

There will be a point (as you turn it) where it evens up depending on the fov.

[Davey-T]

Just had another play with this, if I rotate the camera the over/under exposed bits go round with it, never noticed a problem on DSOs or planets but I guess the Sun shows it up more,

Looks like a new camera is on the cards, so what is the perceived wisdom of SGL members on the "best" camera for Solar ?

Dave

[Steve Ward]

Toss up between the ASI120 Mono and the QHY5-II Mono at the lower end .

[SimonfromSussex]

Dave, are you using a double stack scope?

If so, have you tried rotating the front etalon (not the camera), just unscrew it a bit? 

There is a sweet spot and by rotating the front etalon it moves the sweet spot. You might then need to then retune using the screw. 

[Davey-T]

Dave, are you using a double stack scope?

If so, have you tried rotating the front etalon (not the camera), just unscrew it a bit? 

There is a sweet spot and by rotating the front etalon it moves the sweet spot. You might then need to then retune using the screw. 

Using LS6O DS  with internal pressure tuner and front mounted etalon, tried rotating the front mounted one as per you're suggestion but it didn't seem to alter the problem.

Will try retuning again when the sun comes out, gone cloudy now.

Did manage a quick vid of the prom using 2X barlow so will see how it turns out.

Dave

[Davey-T]

Toss up between the ASI120 Mono and the QHY5-II Mono at the lower end .

And at the money no object end ? 

Dave

[Steve Ward]

http://www.edmundoptics.co.uk/imaging/cameras/usb-cameras/point-grey-grasshopper-3-high-performance-usb-3-0-cameras/88055

[Davey-T]

http://www.edmundoptics.co.uk/imaging/cameras/usb-cameras/point-grey-grasshopper-3-high-performance-usb-3-0-cameras/88055

Can't spend that much as there's  Canon 400 lens at Park Cameras calling my name

How about a DMK 41 ? remember a post about it a while back.

Dave

[Uplooker]

You could save yourself some money and ensure that the camera is orthogonal. You could even just slip a bit of card between the camera nosepiece and the draw tube.

Ian

Sent from ma fone using Tapatalk

[Steve Ward]

DMK41 ... big chip but very slow frame rate ... better with one or other of the first two ... 

[Davey-T]

You could save yourself some money and ensure that the camera is orthogonal. You could even just slip a bit of card between the camera nosepiece and the draw tube.

Ian

Sent from ma fone using Tapatalk

Tried tilting the camera in the BF tube, didn't seem to help but only had a quick try before the clouds rolled in, will try again tomorrow.

Dave

[Montana]

I would say that the tuning is off from first glance at the image, but then if you say the overexposed bit goes round with the camera, then the camera is at fault somehow. It's a great shot though :)

The DMK41 is a great camera, I've never had a problem with frame rate it and I still use it, it is a great all rounder. It is an old model and there are faster more expensive things out there but for a budget it's great.

Alexandra

[Davey-T]

Just had another go at this problem and I think Simon is right, single stack pic is OK, double stack pic shows the problem, started raining now so have to try tomorrow.

Just had a look and there doesn't appear to be any way to rotate the front Etalon as it's threaded onto the front of the scope the only way to rotate it is by loosening it

Dave

  

[SimonfromSussex]

Hi Dave,

DrRobin gave me some great advice and suggested I got one of these:

https://www.teleskop-express.de/shop/product_info.php/info/p4295_TS-360--Rotation-with-M90-thread.html

Thread all about it:

http://stargazerslounge.com/topic/211645-lunt-60mm/?p=2264504

Not cheap but makes tuning the front etalon so much easier. 

You can just undo it first of all though and see if that solves your problem?

Tune the first etalon first to the best place without the double stack. Then add the second etalon. I found as you turn it the sun goes dark in some positions and there is an obvious sweet spot.

[Davey-T]

Bit confused, it says for rotating the focuser, does it fit the front of the LS60 and front mounted 60 etalon ?

Does introducing the extra 10mm cause any problems ?

Dave

[Davey-T]

Just had another play between the clouds, the single stack is ok but the double stack is rubbish, tried rotating the front etalon but didn't seem to help.

Stretched the red in D/S one to exagerate the problem also seems to be some sort of horizontal lines on it.

Just stacked in RG6 no wavelets best of 1500 frames.

Dave

 

[SimonfromSussex]

It fits between the front etalon and the main scope. Screws on the front of the main scope and the second etalon screws into it.

Mind if rotating the second etalon didn't help then it's not worth the spend?? You should definitely notice a change in the image though as you rotate it? With or without the adapter.

The only other thing I can think of is on mine the second etalon creates two reflections along side the main image of the sun just outside my fov.

These reflections look like a degraded image of the actual well tuned one. Have you tried panning the scope up and down or left and right to make sure you are on the real image rather than a reflection?

You should also find that as you rotate the second etalon these reflections change position. You need to get them out of the fov obviously. Try it with a 12-14mm eyepiece perhaps?

[Davey-T]

Thanks Simon, not fussed about the expense, just need to be sure it fits the LS60 and 60 front etalon as it doesn't appear to be the purpose it's made for.

Got clouded out yesterday and not looking good at the moment, need a nice sunny day to play about some more.

How sensitive is the "sweet spot" ? ie; how much do I rotate it to see an effect ? tried rotating it 45 degrees at a time yesterday, is this too much ?

Dave

[SimonfromSussex]

Using an eyepiece (which is the only way I have done it) it's a really noticeable change from even the slightest rotation.  

I wont pretend its not fiddly as it is and takes a little while to find the best spot but its very obvious when its good and when its not using surface detail.

My work flow was:

1) Remove second etalon and tune main scope to best place.

2) Screw on second etalon and rotate second etalon until reflections leave field of view and the image looks brightest/best. If we call the position the 2nd etalon was screwed in tight to the main scope as "home" I found 120deg clockwise from home made it really dark and faint surface detail. For me about 30deg anticlockwise from home is the best spot (i.e. 180deg from the worst spot) but it will almost certainly differ from etalon to etalon so yours may be totally different.

3) Tune second etalon using dial on side.

4) Try rotating second etalon to improve picture.

5) Try retuning second etalon using dial on side to improve picture.

6) Repeat steps 4&5 until you have the best picture but keeping reflections from fov. It's a bit of trial and error and you may find you have to go back to a previous position that is best. 

Hope the clouds clear for you and you can give it a go!!