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ABC's of using the solar filter

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15 replies to this topic

#1 Old Don

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Posted 17 September 2019 - 05:09 PM

Is there a discussion on this forum for using the Questar solar filter?

If not, how about a discussion/guide for a beginner.



#2 Gregory Gross

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Posted 17 September 2019 - 07:21 PM

Tell us first about whether you have an off-axis or full-aperture filter or whether you have a finder solar filter installed on your Questar.

 

You may also consider contacting Questar for instructions on how to use your scope for solar observing. I tend to exercise extreme caution with solar observing and would prefer to follow instructions that come directly from the manufacturer.



#3 Optics Patent

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Posted 17 September 2019 - 08:00 PM

Important warning: Do not stare into sun with remaining eye!

#4 RobertPettengill

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Posted 17 September 2019 - 09:19 PM

Questar solar filters have an OD of 4.5, most solar filters for visual use are OD 5, this means that the full aperture Questar filter is on the bright side.  I find it a bit uncomfortable to use visually. The faster exposure time is an advantage imaging.  The sub-aperture filter is quite comfortable visually, but has noticeably less resolution when imaging.

 

My note comparing white light solar filters may be helpful:

http://astronomy.rob...ghtFilters.html

Any differences in image quality between the full aperture Questar, Baader, and Thousand Oaks filters was small compared to the seeing variations from shot to shot.

 

;rob

 

P.S. If the Bristol Spline screw that holds the flip up sun filter for the finder scope becomes loose, it can flop down and let direct sunlight through to the eyepiece when looking through the finder.  Happened once setting up for a solar viewing and scared me.


Edited by RobertPettengill, 17 September 2019 - 09:24 PM.


#5 Optics Patent

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Posted 17 September 2019 - 10:19 PM

To fine tune the safety advice for the finder, the Bristol screw does not affect the finder filter friction. Tightening it only secures the ring to the finder (and then cracks the ring when over tightened). The motion and stability of the finder filter is adjusted by a second screw that is accessible only when the finder filter assembly is (easily) removed.

Edited by Optics Patent, 17 September 2019 - 10:19 PM.


#6 Old Don

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Posted 18 September 2019 - 01:17 AM

I have an off axis filter and a solar filter on the finder. 

I am reluctant to just pop them on and start to view the sun.

A routine to follow would be very helpful.

Will I be able to view Mercury’s transit?

Thank you



#7 RMay

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Posted 18 September 2019 - 02:00 AM

Hey hi Don, start with the solar finder in place >and< the off axis solar filter in place of the front objective, so your eyes and the scope are totally protected. With the finder solar filter in place, keep the scope pointed down and then slowly sweep up towards the Sun. Everything in the eyepiece will be black but at the finder magnification you’ll see the disc of a very deep orange sun against the black background of the filter. Once it’s centered, you can flip to magnification. That should do it.

As others have noted, however, make sure that when your finder solar filter is in place, there’s enough tension to keep it securely in place and not fall down.

By all means, post any comments or questions.

Cheers,

Ron

#8 Erik Bakker

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Posted 18 September 2019 - 02:29 AM

I have an off axis filter and a solar filter on the finder. 

I am reluctant to just pop them on and start to view the sun.

A routine to follow would be very helpful.

Will I be able to view Mercury’s transit?

Thank you

What you have is fine Don and will easily show you Mercury's transit.

 

Just pop/screw them on, make sure they are solidly attached to protect your eyes and enjoy the views. It's that simple.

It's a good habit to first cover the finder with it's solar filter and then screw on the solar filter for the aperture of scope. In that order you won't forget to put the tiny filter on the finder.

 

For more solar detail and the ability to magnify more, you can always add the full aperture solar filter later if you feel the need.



#9 BillHarris

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Posted 18 September 2019 - 04:01 AM

The "OD" that Rob mentioned was "optical density" (the absorbance of the filter) and not "outside diameter".

If the Questar solar filter is uncomfortably bright for visual use, I suppose that a ND (neutral density) filter could be screwed onto the eyepiece. I wonder what density filter would be used to bring the overall density from 4.5 to 5.0? Since the OD scale is not linear, I figure it would be a stretch to simply add an ND 0.5 filter.

One thing I find helpful in aiming the scope at the Sun is to bring a 12"x12" white card and "minimize" the scope's shadow on the card.

#10 Old Don

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Posted 18 September 2019 - 04:48 AM

Thanks Ron and Eric.

That is exactly what I wanted to hear before trying to observe.



#11 Optics Patent

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Posted 18 September 2019 - 05:48 AM

Sunglasses are an aptly named brightness reducer. I’ve never found the image to be uncomfortably bright, however.
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#12 Old Don

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Posted 18 September 2019 - 01:52 PM

What is your preferred mm eyepiece?
Any tips for the initial alinement other than sun glasses?

#13 Old Don

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Posted 18 September 2019 - 01:54 PM

What is your eyepiece of choice?
Other than using sunglasses, any tips for initial scope alignment?

#14 RMay

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Posted 18 September 2019 - 02:33 PM

I use a Q 16mm or a TV 19mm wide field. Solar viewing is really sort of point and gaze... keep the solar filters in place...

#15 Antares

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Posted 23 September 2019 - 07:25 PM

FYI: I own a 1994 Questar Standard. My first full aperture solar filter was uncomfortably bright as BillHarris describes. I contacted Questar and described the problem. They were willing to replace the filter, which they did. Ever since then, I’ve had a full aperture solar filter that was perfectly bright for both visual and photographic work. Although this was many years ago, I would guess that Questar might still be willing to do the same again for another Questar owner.

Bart

#16 Optics Patent

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Posted 23 September 2019 - 08:48 PM

My alignment method is to adjust RA until the shadows of the declination discs and ring disappear. Then adjust declination until the barrel shadow is minimized and other aspects of shadow and reflections are apparent.


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