dont know what I'm doing wrong

[shamba504424]

Hello

Whenever I take a solar capture and look at in Autostakert or Registax the eastern side of the image or around about twenty past on a clock face is over exposed to the rest of the image and really dont understand why it is so if anyone has ideas I would be really grateful.

Thanks 

Tony

[Davey-T]

What are you capturing with ?

Dave

[shamba504424]

Hi Dave

I have been using Sharpcap but am going to try using Firecapture

Tony

[shamba504424]

Hi Dave

If you mean what equipment its a Lunt ls60 bf1200

Tony

[Lowjiber]

Switching to FC is not going to fix a partial over-exposure issue.

Can you post a typical image to give us an idea of just how over-exposed it is?  Typically, the sun is brighter toward the center of the sphere.

When shooting the surface, adjust the exposure and gain to attain between 60 & 70% on the Log scale.

[shamba504424]

Hi John

Thanks for replying and here is one of my images,the over exposure always seems to be in the same area and as I say I dont know why this should be.

[Davey-T]

Have you checked down the front of the BF1200, they can fog up causing uneven illumination.

See this thread.

Dave

 

[shamba504424]

Hi Dave

 thanks for your reply and no I haven't checked that but the scope is only about 4 weeks old so could this happen to an almost new scope?

Tony

[Lowjiber]

Hi again, Tony

Your details are amazing in the properly exposed (3/4) of the disk.  Thanks for posting it.

I've had a similar problem with my Lunt 60PT/BF1200 in the past.  Both times it was caused by the etalon being a little slow to completely adjust to my tuning settings.  (I know this shouldn't be the case, but here's what I did.)

I removed the piston assembly to clean and re-lube the piston/o-ring.  The lube that was present beforehand had become slightly "stiff" with use.  By "servicing" the piston assembly, I immediately saw (felt?) a smoother movement when adjusting.  Like your disk above, I was so close with the correct tune, but the etalon was reacting very slow to my adjustments causing my heartburn.

I also developed the habit of cranking my tuner knob completely in (clockwise) and making my tuning adjustment by backing off the knob (reducing the pressure inside the etalon, vice increasing it by turning clockwise) to make my adjustment.

The bottom line is the etalon is always "behind" your knob setting by just a bit... taking too much time to "catch-up".   By cleaning/re-lubing the piston and turning counter-clockwise to slowly make the adjustments, the etalon is able to react better to the very fine adjustments needed to level the histogram.

I know that may seem like voodoo, but it works.

Following up on the above, I'll add that I crank my tuner knob completely clock-wise and let the scope set for about five minutes before beginning the (outward) adjustment.  That "habit" has served me well with two LuntPTs over the past five years.

I'll add that a perfect gradient adjustment will be when the center of the sun is slightly brighter than the surrounding surface... revealing the sphere-like nature of the sun.

Hope that helps.

Clear Skies

[shamba504424]

Hi John

Thanks again for replying,such helpful people on this site.

Well  only just got the scope at the end of August brand new,what is concerning me is that I have just bought the zwo asi174mm in the last week so have sent off a couple of pictures to the supplier together with detail of the problem so am waiting to hear back from them as it could be a camera issue, dont seem to have a problem with my zwo asi120mc-s

Clear Skies

Tony

[shamba504424]

Hello again John

Well I heard back very quickly from FLO and the guy there said he had a similar problem and the answer he gave was most likely the tuning which is exactly as you told me John,going to take all your advice and apply when the sun comes out again which isn't often when you live in the north of England.?

Thanks again

Tony

[Lowjiber]

Tony, I'm glad you got a fast reply from FLO.  They're a great company to deal with.

I use the ASI174MM monochrome cams (I have two of 'em, both cooled.) all the time.  If, like me, you're using SharpCap, try to find a copy of Version 3.0, or earlier.  With the latest version, Sam Wen (the owner of ZWO) refused to let SharpCap include gamma controls for his cameras.  Gamma control can be of great benefit, especially to a new solar imager... lower gamma (~20) can enhance surface details while settings around 65 can help with finer prom details.

You'll get there... not to worry.?  There are a lot of very good imagers here that will help you climb the learning curve.

Clear Skies

[shamba504424]

Thank you so much John,will see if I can track it down.

Clear Skies

Tony

[Pete Presland]

Good to hear your getting sorted Tony. Tuning any of the Solar scopes out and getting the right "sweet spot" is the key to a good image. 

[Davenn]

On ‎22‎/‎10‎/‎2018 at 02:57, shamba504424 said:

Hi John

Thanks for replying and here is one of my images,the over exposure always seems to be in the same area and as I say I dont know why this should be.

Yeah, I have always seen the same thing LUNT LS60THa using either the ASI178MC or the ASI1600MM

 

On ‎23‎/‎10‎/‎2018 at 00:07, Lowjiber said:

Hi again, Tony

Your details are amazing in the properly exposed (3/4) of the disk.  Thanks for posting it.

I've had a similar problem with my Lunt 60PT/BF1200 in the past.  Both times it was caused by the etalon being a little slow to completely adjust to my tuning settings.  (I know this shouldn't be the case, but here's what I did.)

...... big snip.........

Hope that helps.

Clear Skies

 

HI John

interesting comments ....... but wouldn't your described situation only occur immediately after you had done tuning ?

I have found that it doesn't matter if tuning has been done recently or not.  What I have discovered is that the change of brightness changes as I move the

sun's image across the field of view of the camera ... That is, I can move the sun's image to a position on the sensor where it is reasonably evenly exposed

across the entire disk.

 

I would almost put money on it that that brighter region on his image is roughly equal to the central area of the CCD sensor chip

as that is what I observe with my system

 

NOTE ......  this is ONLY a imaging thing  as with Tony's example image ...... when looking visually through the eyepiece .... the brightness is reasonably

flat across the disk .... yeah ok, a little brighter in the central area but not by a lot

 

Dave

Edited October 25, 2018 by Davenn

[Merlin66]

Caused by the “sweet spot” in the etalon tuning.

Get the best balance you can....

 

[Macavity]

The way I solve this sort of thing is to "clock" the diagonal / camera with respect
to the OTA. With a T2-based thread system, the following rotator-adapter helps...
Once you have a more symmetric image rotate the OTA in the ring to look nice! ?
(It doesn't actually matter whether the tuner points to the left, right, up or down)

https://www.teleskop-express.de/shop/product_info.php/language/en/info/p5547_TS-T2-Thread-360--Rotation-and-Quick-Changer---5-5mm-short.html

Edited October 25, 2018 by Macavity

[shamba504424]

Hello all and thanks for your comments,Macavity I'm not sure I undertand,do you mean just physically rotate the camera in the eyepiece,wouldn't this just move the over exposure to another place going by what Dave has suggested regarding the sensor chip,dont really know if I have fully understand the last couple of replies.

Tony

[Macavity]

No guarantee... but my PET theory is that the reason such images are produced
is the tuned optical axis is not aligned with the physical axis. Bit like collimating
a Newtonian Reflector (or indeed refractor!) to ensure that things "all line up"! ?

Not sure of the precise conficuration of your scope, but to see if this might help 
try rotating / clamping (waggling) the (scope side of the) diagonal through the
various angles about the OTA. A fully T2 threaded system later just allows you to
rigidly clamp the scope/diagonal when you discover the optimum orientation! ?

Edited October 25, 2018 by Macavity

[shamba504424]

Thanks again

Understand what you mean and its certainly worth a try.

On another topic just wondering about greasing the pressure tuner,got some 100 percent pure silicone grease and was curious if this is ok to use and how much to use

Tony

[Davey-T]

7 hours ago, shamba504424 said:

On another topic just wondering about greasing the pressure tuner,got some 100 percent pure silicone grease and was curious if this is ok to use and how much to use

You need something with a high melting point as you don't want it running everywhere and silicone grease tends to creep, I used red rubber brake grease when I regreased my LS60 but it may invalidate the warranty so best consult Lunt before you touch it, it shouldn't need regreasing for a few years from new anyway.

Dave

[shamba504424]

Ok thanks for your reply Dave

Tony

[Altocumulus]

On 23/10/2018 at 14:16, Lowjiber said:

Tony, I'm glad you got a fast reply from FLO.  They're a great company to deal with.

I use the ASI174MM monochrome cams (I have two of 'em, both cooled.) all the time.  If, like me, you're using SharpCap, try to find a copy of Version 3.0, or earlier.  With the latest version, Sam Wen (the owner of ZWO) refused to let SharpCap include gamma controls for his cameras.  Gamma control can be of great benefit, especially to a new solar imager... lower gamma (~20) can enhance surface details while settings around 65 can help with finer prom details.

You'll get there... not to worry.?  There are a lot of very good imagers here that will help you climb the learning curve.

Clear Skies

Old thread, I know - but regarding Sharpcap and the gamma option not being available in the later versions on account of ZWO - I notice ASICAP has an image gamma setting. mmmm or am I misreading what the asicap setting does?