Search found 247 matches

by george9
Thu Oct 06, 2022 12:16 pm
Forum: Solar Scope Modifications
Topic: Etalons Lunt LS80T-Ha and DSII - focal length
Replies: 2
Views: 68

Re: Etalons Lunt LS80T-Ha and DSII - focal length

I don't know the actual numbers, other than that it is designed for working at f/7 and works well in my f/7 AP155, so they can't be too far from that. (So somewhere around 7*52 for the primary and somewhere around 7*35 for the DSII.) I guess someone would have to disassemble to get the actual number...
by george9
Tue Oct 04, 2022 12:35 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Thanks so much for the SPOD, Alexandra! George
by george9
Mon Oct 03, 2022 5:58 pm
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Alexandra, as James points out, you have a great start. Adding a field stop should feasible. You can iterate on the rest as needed. The big challenge is the cost and temperature regulation of the 5303A filter. But there are other fun things you can do with a just a little tinkering. For example, ima...
by george9
Mon Oct 03, 2022 5:58 pm
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

Alexandra, as James points out, you have a great start. Adding a field stop should feasible. You can iterate on the rest as needed. The big challenge is the cost and temperature regulation of the 5303A filter. But there are other fun things you can do with a just a little tinkering. For example, ima...
by george9
Mon Oct 03, 2022 11:30 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Hi. I am talking about Appendix 2 on page 234 of the Solar Astronomy book English version. I know there were additions, so not sure if the French version has Appendix 2. I know an update to that is planned. I am using a Celestron FirstScope 80mm (910mm f.l.). I removed the objective and built a cell...
by george9
Mon Oct 03, 2022 11:30 am
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

Hi. I am talking about Appendix 2 on page 234 of the Solar Astronomy book English version. I know there were additions, so not sure if the French version has Appendix 2. I know an update to that is planned. I am using a Celestron FirstScope 80mm (910mm f.l.). I removed the objective and built a cell...
by george9
Mon Oct 03, 2022 1:37 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Right. I use 304A when I cannot tell which way my coronagraph is oriented and I don't want the Sun to drift out from under the cone. I get a shot in H-alpha, compare that to 304A to figure out my orientation, then when I shoot at 5303A, I can flip the 171A image around to the right spot without chea...
by george9
Mon Oct 03, 2022 1:37 am
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

Right. I use 304A when I cannot tell which way my coronagraph is oriented and I don't want the Sun to drift out from under the cone. I get a shot in H-alpha, compare that to 304A to figure out my orientation, then when I shoot at 5303A, I can flip the 171A image around to the right spot without chea...
by george9
Sat Oct 01, 2022 11:24 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Yes exactly, James! That yellow image in my first post is SDO 171A. It's been really helpful that SDO images the corona constantly, so that when you look in the scope and think you see something, you can go right on your smartphone and check if the satellite shows anything bright in the same area. I...
by george9
Sat Oct 01, 2022 11:24 am
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

Yes exactly, James! That yellow image in my first post is SDO 171A. It's been really helpful that SDO images the corona constantly, so that when you look in the scope and think you see something, you can go right on your smartphone and check if the satellite shows anything bright in the same area. I...
by george9
Fri Sep 30, 2022 8:47 pm
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

530.3nm is Fe XIV, or very ionized iron, reflecting the super high temperatures of the corona. I just read that it was ascribed to a hypothetical element called coronium until 1939, when the iron origin was figured out.

George
by george9
Fri Sep 30, 2022 8:47 pm
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

530.3nm is Fe XIV, or very ionized iron, reflecting the super high temperatures of the corona. I just read that it was ascribed to a hypothetical element called coronium until 1939, when the iron origin was figured out.

George
by george9
Fri Sep 30, 2022 10:37 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

It took me about a year, and I had Klaus helping me out. I would have some issue, and he would recognize what was going wrong, or at least have some suggestions. Some basic optics knowledge helps. Christian's Solar Astronomy book has general instructions how to make one and is the best current sourc...
by george9
Fri Sep 30, 2022 10:37 am
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

It took me about a year, and I had Klaus helping me out. I would have some issue, and he would recognize what was going wrong, or at least have some suggestions. Some basic optics knowledge helps. Christian's Solar Astronomy book has general instructions how to make one and is the best current sourc...
by george9
Fri Sep 30, 2022 2:09 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Here is a CN post that describes converting a Baader prominence viewer to a coronagraph: https://www.cloudynights.com/topic/788861-progress-on-coronal-viewing/?p=11357452 Swapping the 5303A filter for the H-alpha filter is one part. The main addition is a field stop between the end of the cone and t...
by george9
Fri Sep 30, 2022 2:09 am
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

Here is a CN post that describes converting a Baader prominence viewer to a coronagraph: https://www.cloudynights.com/topic/788861-progress-on-coronal-viewing/?p=11357452 Swapping the 5303A filter for the H-alpha filter is one part. The main addition is a field stop between the end of the cone and t...
by george9
Thu Sep 29, 2022 5:24 pm
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Thanks. Yes, the sky has to be pretty clear. Just put the Sun behind an object, usually your thumb, and see if you can tell the Sun is hidden due to local sky brightening. If the sky looks deep blue to the edge of the Sun, you have a good day. I cannot find a SC post of my most recent coronagraph, b...
by george9
Thu Sep 29, 2022 5:24 pm
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

Thanks. Yes, the sky has to be pretty clear. Just put the Sun behind an object, usually your thumb, and see if you can tell the Sun is hidden due to local sky brightening. If the sky looks deep blue to the edge of the Sun, you have a good day. I cannot find a SC post of my most recent coronagraph, b...
by george9
Wed Sep 28, 2022 10:46 am
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Re: Corona from 24 September 2022

Thanks very much. I will point out that I learned how to do it from Klaus160. And Christian's book was helpful with its easy-to-use formulas for the optical design. (And we all owe Lyot.) The hard part was debugging all the stray light in the system.

George
by george9
Wed Sep 28, 2022 10:46 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Re: Corona from 24 September 2022

Thanks very much. I will point out that I learned how to do it from Klaus160. And Christian's book was helpful with its easy-to-use formulas for the optical design. (And we all owe Lyot.) The hard part was debugging all the stray light in the system.

George
by george9
Wed Sep 28, 2022 2:15 am
Forum: SPoD Archive
Topic: Corona from 24 September 2022
Replies: 38
Views: 87

Corona from 24 September 2022

Here is a view from Pennsylvania last Saturday at 2300 feet on a very clear day. This is my 50mm coronagraph, 5303A filter, ASI1600 Pro camera, 60 sec video. The second image is a blowup of the biggest area. You can easily see the loop structures. At bottom in yellow is the SDO 171A satellite image ...
by george9
Wed Sep 28, 2022 2:15 am
Forum: This is SolarChat !!
Topic: Corona from 24 September 2022
Replies: 42
Views: 569

Corona from 24 September 2022

Here is a view from Pennsylvania last Saturday at 2300 feet on a very clear day. This is my 50mm coronagraph, 5303A filter, ASI1600 Pro camera, 60 sec video. The second image is a blowup of the biggest area. You can easily see the loop structures. At bottom in yellow is the SDO 171A satellite image ...
by george9
Tue Sep 27, 2022 8:02 pm
Forum: Solar Scope Modifications
Topic: Lunt Cak B1200 mod question
Replies: 15
Views: 335

Re: Lunt Cak B1200 mod question

This answer is for imaging, not visual: I see Andover Corporation has a new hard-coated 25mm filter centered at 394nm with 10nm FWHM and very steep sides for just $159. It is OD4 from 200 to 1200nm other than over 90% transmission near 394nm (both H and K lines seem to get through over 93% on their ...
by george9
Wed Sep 21, 2022 8:31 pm
Forum: Solar Scope Modifications
Topic: AP155 and LS80 DSII
Replies: 32
Views: 790

Re: AP155 and LS80 DSII

I just drew a diagram to check my work. If you push the negative collimation lens toward the objective, then you no longer have a collimated system. The top ray trace is collimated. The distance, x, is the same from the collimation lens to F1 and to F2. Their focal ratios are about the same, around ...
by george9
Wed Sep 21, 2022 5:31 pm
Forum: Solar Scope Modifications
Topic: AP155 and LS80 DSII
Replies: 32
Views: 790

Re: AP155 and LS80 DSII

Sorry, I should have been more clear. My negative collimating lens is attached to my etalon. When I say I moved the etalon 20mm closer, I really meant I moved the negative collimating lens 20mm closer. That changes the effective focal ratio seen by that lens. It looks like a longer focal ratio becau...