Kitsunegari

2 hours ago, michael.h.f.wilkinson said:

Sounds like some internal reflection of flat optical surfaces in the optical train. I do remember having some internal reflection issues in my Coronado scope, but not in my earlier Lunt LS35THa 

IT is a reflection off the televue optics and explore scientific optics because it happens on the moon with zero filters added.  It goes away when you remove the second lens in the powermate, indicating that its the second lens....

SDO | Solar Dynamics Observatory (nasa.gov)

4 hours ago, Ken82 said:

As mentioned previously strehl ratios are mostly measured in the green spectrum for visual use.

From what i have learnt above 90 strehl is really fine for astrophotography.

I have seen some certificates from LZOS scopes with strehl of 98% in green and 86% in blue.

I believe a strehl of 0.8 is diffraction limited so any aberration error will be smaller than airy disk. And of course strehl plays no role in chromatic aberration!

Ken 

 

 

If i am not mistaken ,  LZOS built  the best lens ever manufactured outside of a government agency.      I would love to see what adding LIDAR could do for a cnc milling/polishing process.    Probably would never need an interferometer report....

Especially after the magic formula was cracked   How One Mathematician Solved a 2,000-Year-Old Camera Lens Problem (popularmechanics.com)

i am envious of your 2.5x powermate.

Mine is useless and applies a Large circle dead center in all my images,  in fact  70% of televue powermate 2.5x owners have this problem when imaging and are quite upset about it...  (not just the sun, its there on the moon too)

Also; my explore scientific 3x tele-extender.  has the same problem.      Whoever is building  these things are missing an important aspect of the design,  i am starting to wonder if the products are actually counterfeit?

Are you using an extension tube at all on the back of your powermate?  

And yea, People really did use a string as a focuser...  

The Era of Long Telescopes | SpringerLink

6 minutes ago, John said:

Also, what has this to do with strehl ratio ?

 

Strehl ratio changes with color.  

Usually telescopes are rated for one color of light,  typically green.             The hard truth here, is that a triplet / quadruplet telescope that was designed for visual use at 450nm -680nm  maybe absolute garbage at 390nm.         (very important to solar observation)

Spectrally a little different for mirrors because they perform the most  amazing at blue light,   however spherochromatism is going to make or break your enjoyment with imaging and high magnification....            

3 minutes ago, John said:

Well, for nighttime observing I've found that light shrouds are needed otherwise the wonderful optics show lowered contrast due to ambient light intrusion.

The solar image you post are H-alpha I believe - what H-a filter do you use to get them ?

 

Works great for night time too    

The first image is h-alpha,  the second is calcium k-line.

For the first image its a modified Lunt LS50C etalon that i put in a shroud for internal use. (normally is intended for external)

That particular calcium filter is something that I developed and cannot be purchased (was my own development).    Its called a Skybender.

4 minutes ago, John said:

This thread is 14 years old !

I'm amazed that the mount, and EQ5 clone, handles such a large, long, heavy optical tube

 

I love looking at old posts and reviving them!  Just seeing  the stargate telescopes by explore scientific really shows not much is needed other than the optics!

I do not have any problems with the mount unless the wind kicks up to about 20mph,  the entire scope weighs about 11kg.  

Here is my "big silver shiny zero baffle scope" that i point at the sun and get the images below.. .         250 years ago people literally mounted  huge optics to a roof, tied a string to it, and literally tied the eyepiece to a string dangling from said roof optic. and brought it to their eye.  No tube. No baffles. Nothing but 20 feet between them and the optic.     You would be pretty surprised how good a 4000mm focal length optic pointed at the moon looks through an eyepiece attached to a string......

Strehl ratio is the division line factor of  "are you ever gonna take a picture or just use a 25mm eyepiece."               

13 minutes ago, Ibbo! said:

That would be OK for me as I stand 😄

 

Would you stand for a solid hour straight hunched over to look at a computer screen?       

Hey i just noticed you have a bresser 127/1200 ach.    That telescope is identical to my explore scientific firstlight 127.     HAve you tried it on your calcium filter yet?     If the objective is anything like mine, its gonna be greater than .85  strehl at wavelength.     

i know what you mean about forgetting stuff, and leaving equipment unattenteded.     I have the same issue right now,  need to carry my mount 100 yards away from the house, then the telescope. Then I have to load up a wagon to carry the batteries ,cables, controller, computer etc....     When i forget to put something on the wagon, its certainly is bothersome.

Today i forgot the chair!!!!  

Shot through trees and horrible sky.  The sun is very low and is almost not worth me going out to image;  However I  insist to persist!  It is a shame to lock up thousands of dollars in equipment with such a great sunspot to record.

Despite how menacing this spot looks,  it appears to be quite docile.     

nice!

a dual light bridge, nice!

looks like it is about to become two spots, and then release an m-class flare

Thanks for the kind words everyone.

lookin good.   Seems like Co-vid-19 was literally designed to keep average working class humans on the earth while the elite get to fly on rockets and spaceplanes.....

First time i have ever recorded these.   The bright pins inside the sunspot umbra.

Enjoy!

updated to 85 frames,  more frames still prcocessing.

20 minutes of time represented here.

127mm x 1200mm + meade 2x shorty.

Pefect outside before head out he door for work .   Crawled out of bed and snapped 150 frames. Something big  happenend about 5 minutes after i i ran out of disk space

off to work!  will post my 2x barlow timelapse when i get home.

IF you never got a chance to witness this,  i believe on this day ;  one of the biggest coronal mass ejections ever recorded on video.

There were aurora borrealis visible in all 50 states in north America. Including hawaii.   I saw them here in illinois, very vividly around 1030pm at night for about 20 minutes total. 

The new  region is providing  some of the greatest momentum we can see.  (expect an m-class flare sometime this week.)

Get your cams out,  point it at the new region, set your full disk cadence to have a 3 second delay.

Set your high magnfiication cadence to 1 second delay.

Good luck for anyone that gets enough sun to get some great video of this.   I may intentionally bail out at work early just to get some of that action....     (oh no ! Solar diarrhea, sorry im going home!)

realistically you are going to need more than a canon 800mm lens.

IR/UV cut filter on the objective is a must.

2x teleconverter is a must.

Name on the lens doesnt mean much, and picture quality is never ever ever reflected by price in the camera industry.       How well does  your camera focus on the moon?   That is kind of more important than the canon lens.    

So to answer your question.

The canon lens is only 400mm better.     So this factor alone makes it.    

If you want to capture magnetic field lines you are going to need something with great fine focus.

What part of the eclipse is your main goal?  That is also important because it does take along  waiting for maximum darkening.   That totality is where everyone gets confused too, suddenly you forgot to adjust a setting.   (alot of people use two cameras because of this)

Dont forget you need a neutral density,  probably nd500 minimum

28 degrees outside at 10am,      Worst seeing conditions, restricted my use of magnification.

these things have a tendency to go hurl thick dark jets out of them,  nice shot!