Space blanket as a Filter

[EdwinHubble2023]

Dear Astronomy Community:

Can anyone use the material from a Mylar space blanket as a neutral density filter for solar observing?

Also, can anyone spin a container of, say, an epoxy resin, so that a parabolic surface in form congeals to form a mirror blank?  Perhaps this idea might yield mirror blanks that are lighter than conventional glass mirror 

blanks and have a smaller coefficient of expansion than conventional glass mirror blanks.  Thank you.

 

 

                                                                                                                                                                                                   Best regards,

                                                                                                                                                                                                   Carl Mesaros    

[Cornelius Varley]

6 minutes ago, EdwinHubble2023 said:

Can anyone use the material from a Mylar space blanket as a neutral density filter for solar observing?

Don't even think about it. Only ever use the correct materials designated for use for solar observing.

[wulfrun]

I don't think you can use a space blanket as a solar filter, despite what you may think. The film sold for that is aluminised on both sides, meaning a pinhole in the coating on both sides in the same place is nearly impossible. Space blankets are aluminised on one side, as far as I can see. That leaves a serious risk.

[Stu]

20 minutes ago, EdwinHubble2023 said:

Dear Astronomy Community:

Can anyone use the material from a Mylar space blanket as a neutral density filter for solar observing?

Also, can anyone spin a container of, say, an epoxy resin, so that a parabolic surface in form congeals to form a mirror blank?  Perhaps this idea might yield mirror blanks that are lighter than conventional glass mirror 

blanks and have a smaller coefficient of expansion than conventional glass mirror blanks.  Thank you.

 

 

                                                                                                                                                                                                   Best regards,

                                                                                                                                                                                                   Carl Mesaros    

As others have said, just don’t.

Properly rated solar film is cheap to buy, so there is no need to take such risks.

[RT65CB-SWL]

Hi @EdwinHubble2023 and welcome to SGL. 

Do yourself a favour and buy a sheet of Baader Safety Solar Film. Apologies in advance if I appear blunt and/or rude [I have been up since 2:00am]… and remember to make a solar filter for your finder and/or guidescope. Also do examine all solar filters before and end of each solar session for any defects.

Edited May 1, 2023 by Philip R

[saac]

5 hours ago, EdwinHubble2023 said:

Dear Astronomy Community:

Can anyone use the material from a Mylar space blanket as a neutral density filter for solar observing?

Also, can anyone spin a container of, say, an epoxy resin, so that a parabolic surface in form congeals to form a mirror blank?  Perhaps this idea might yield mirror blanks that are lighter than conventional glass mirror 

blanks and have a smaller coefficient of expansion than conventional glass mirror blanks.  Thank you.

 

 

                                                                                                                                                                                                   Best regards,

                                                                                                                                                                                                   Carl Mesaros    

No 

and 

No

Jim 

 

[EdwinHubble2023]

I get the message.  Thanks to all of you for your concern for my safety!

[maw lod qan]

The film everyone mentioned is actually very affordable. Compared to your eyesight, it's cheap.

I paid very little for a sheet to make a filter for my 8" reflector and the finder scope. 

 

[Marvin Jenkins]

The best bit is that if you are in the small scope fraternity then the left over off cuts can be used to make solar filters for friends that have small fracs.

I have recently made a solar filter for my 130 newt. The larger off cut made a solar filter for a beginner friends 80mm frac and the little bit left over is going to be used as a filter for my finder with a large surround to block out light.

Win Win Win.

[michael8554]

The University of Arizona manufactures those huge mirrors that professional telescopes have with a rotating glass furnace.

There may be a situation that calls for your lightweight resin version, but I doubt it will  be for astronomy.

Michael

[rl]

Quote

Also, can anyone spin a container of, say, an epoxy resin, so that a parabolic surface in form congeals to form a mirror blank?  Perhaps this idea might yield mirror blanks that are lighter than conventional glass mirror 

blanks and have a smaller coefficient of expansion than conventional glass mirror blanks.  Thank you.

Carl

I used to work for the HIROS astronomy group at Birmingham University in England. 30 years ago we used to spin cast parabolic epoxy mirrors up to 1 metre in diameter for use a flux collectors in long term spectroscopy projects where it was not possible to get enough telescope time for the amount of data needed. These mirrors were not of optical quality but were very light and quite good enough to focus starlight on to an optical fibre which would connect to the spectrometer. They were used to look for low level pulsations on bright stars..basically sound waves bouncing around the stellar interiors in the same way that earthquakes travel around the earth. The photon signal-to-noise needs to be excellent to do this, and you need a lot of data over a long period of time...often months or years. It's called asteroseismology. Most of their work was done on the sun where s/n is obviously not a problem and you can see sound waves with a 5-minute period in real time, but quite a few PHD students tried the far more difficult stellar stuff. 

https://www.birmingham.ac.uk/research/activity/physics/astronomy/solar-and-stellar/helioseismology/bison/background.aspx/background

The epoxy has to be mixed so as to set over a period of 10 days or more..... the room temperature has to be held constant.... the balance needs to be perfect...you need an air bearing to keep the rotation smooth enough...the spin speed has to be tightly controlled.....you need to keep dust off using an electrostatic screen..there is an art to it!