SolarChat!

george9

I realized I made a small error on reporting my measurements. I compared the circular polarizer twice through with a mirror doing it the right way through the polarizer (attenuate reflection) versus the wrong way through the polarizer (don't attenuate). Therefore that 10% transmission is compared to...

george9

When we put two etalons too close to each other but still air spaced and when sufficient titling is not practical, we get reflections between the etalons that looks like a glow around the Sun. We can put a filter between the etalons to reduce the glow since the main image passes through the filter o...

george9

The HRG works because the primary beam goes through once but the reflections pass through three times. So if the HRG reduces the brightness by say 50%, the reflections will be reduced by an additional 75% (87.5% total). (I have not measured the actual HRG transmission.) The circular polarizer exting...

george9

You will need to build something. I use a Lunt HRG cell from which I removed the HRG filter and inserted a circular polarizer in its place. Others have built and used various adapters. Do a Web search on circular polarizer and Solar Chat or Cloudy Nights, and you will find descriptions and photos. I...

george9

Really nice. Some beautiful proms recently. George

george9

I don't have the link right here but perhaps search for BASS2000. George

george9

Yes, great thread. Just to point out that the PST came later. Coronado started with the AS series (e.g., 90 and 60mm) in the late nineties and perhaps earlier models. They were kind of affordable. The ASP-60 was $2650 in 2000. My astro buddy still has our two (we each bought one and took turns doubl...

george9

This is really good. Have you posted the design of your spectro-coronagraph? This may be of interest, by Klaus_160. He took prominence images through a coronagraph and various filters, including no filter. https://www.cloudynights.com/topic/756957-what-filter-do-i-need-to-observe-prominences/ George

george9

I mean in general, Georges experiment looks like fun, but i doubt he got the filter just for to use on the binoculars. Yes, exactly, it was just for fun. I mainly used it on my AP155EDF, usually double stacked with a Lunt DSII unit to get rid of the double limb. It worked great. It ran into prematu...

george9

Here is my 0.3A H-alpha binocular. I made it into a monocular but got to exploit the 15x and image stabilization of the Cannon. Not overly portable, but was fun to put together and view through.

George

george9

That is an awesome comparison. George

george9 · Re: April 20, 2023 total solar eclipse -- Australia Beautiful photo! George

Beautiful photo! George

george9

Hi, Alexandros. Sorry I was away a few days. Plus I don't have solar chat set up to ping me so I have to remember to check. The Lunt 130's primary etalon is big enough that a full disk view should work. I agree with Bob except one correction. The DSII is not purposely tilted by Lunt to shift the ref...

george9 · Re: Sun images 27 December 2022 from Melbourne Australia Really nice. George

Really nice. George

george9

Hi. One question. Is the sweet spot narrow or just off-center? I actually put a homemade copper shim between my primary etalon and the DSII unit to tilt the back, and it probably centers my sweet spot. I originally did it to make the reflections concentric, which in my case seemed to minimize them. ...

george9

Thanks, James. Yes, the Mauna Lao coronagraph is amazing. Too bad it has been down since November for the volcanic activity. It actually gets the K-corona, as opposed to us getting (so far) just the E-corona. You can get better signal-to-noise on the E-corona (with a line filter) versus the K-corona...

george9

I know I have to stop, but I just adjusted the 211A a bit and masked the center. The purple one is the satellite. George

george9

Sorry, here is one more at 211A. This paper demonstrates that it is the best match for 5303A. I find the detail at 3 o'clock and 7 o'clock show this one to be the best.

https://www.raa-journal.org/issues/all/ ... 476626.pdf

George

george9

Here is a better comparison at 193A. A better match than 171A, as Klaus pointed out. George

george9

Here is the Lijiang Observatory conoragraph from the same day. The levels are adjusted slightly to highlight the dim areas. Mauna Loa is down due to the volcano. George

george9

Here is a close SDO image. George

george9

Thanks very much for the comments!

Here is a version where I added a linear gradient on top of the radial one to eliminate the left-right imbalance. I flipped it so that north is up.

George

george9

Was playing with Photoshop gradients to try to dim the center compared to the outside. At a certain point, I end up just highlighting the imperfections.

George

george9

Still working on learning processing. I posted a newer one on CN, but here is a newer newer one. I get rid of fringes by creating 7 zones and moving pieces of the flat to best match that area of the conona image. The subtraction causes enough noise that wavelets don't seem to help afterward. Best to...

george9

Thanks, Valery. I did diagnose that the fringes are coming from within the filters, not between them. Each has its own pattern, one a little dimmer than the other so you don't really notice both (you could see both in some earlier images). Definitely, now that Klaus has shown it is possible, it is c...

george9

Thanks, Valery. I think as illustrated by Stu, I can first improve my processing skills and get more out of the current images. The filter is a double stack of two 2A filters, getting to 1.2A if you multiply the two curves at about 20% transmission. I don't think Andover can do too much better. But ...

george9

Definitely go for the SHG. I would love to when I get more time and if I get better tools. As for a proper location for the coronagraph, it depends on the goal. If it is just to say you can see the corona, then most places can get there. If you want to take better images, then you need a decent loca...

george9

Awesome, Stu. Thank you. Yes definitely more detail without maxing out the brighter parts. My plan is to learn further methods and software. I am unlikely to make another trip over the winter, so plenty of time to learn. FYI, here is a higher resolution but still jpg file of the original stacking. I...

george9

Hi, James. Put the first (dimmer) image above on a computer monitor and step back about 2 or 3 meters. I can see the two brighter regions, and I could just tell that there were streamers in them. No loops seen this time. As for the other regions, it was guesswork. There is a dim green background aro...

george9

Here is one that highlights the dimmer regions.

George

george9

Here is a shot of the corona from yesterday. My 50mm homemade coronagraph, 5303A (1.2A FWHM) filter, ASI1600MM Pro camera. From 3200 feet altitude. It was a pretty clear but not extremely clear day. The Sun was actually relatively quiet on the circumference; those are not strong regions. I could see...

george9

Hi, and happy to help. I would put the new DS etalon about in the middle of its range and then proceed. Once you get it tuned once, you will remember if this DS etalon is best more outward, in the middle, or more inward. Also, I assume you have momentarily unscrewed and re-attached the primary etalo...

george9

On my Lunt LS80 DSII, by trial and error I found that I liked them 180 degrees apart, but there is not too much difference. I also like them apart because I find it easier to tune that way. I generally tune them together, both etalons at the same time. I put them both about where I expect them to wo...

george9

Better things do indeed come through research. I did not solve the fringe problem, but I did figure out the half-fringe phenomenon. As the Sun goes off axis the internal reflection in the objective lens that is normally blocked by the coronagraph's Lyot spot moves to the side of the objective lens a...

george9

An addition. When the Sun is off center, peeking around the cone, there is no fringe pattern. It's not like Newton's rings. There seems to be some fringe component separate from the main stream of light coming through. I need to figure out under which circumstances light causes a fringe pattern and ...

george9

Here is some follow up on the fringes. I reproduced it shining a flashlight into the coronagraph without an objective. The fringes seem to be a property of each filter. One has a straighter fringe and one has a more curved one. The dual fringes in my 9/29 post above is the two filters, not Newton's ...

george9

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...

george9

Thanks so much for the SPOD, Alexandra! George

george9

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...

george9

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...

george9

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...

george9

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...

george9

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...

george9

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...

george9

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...

george9

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...

george9

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

george9

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

george9

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...

george9

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...

Search found 357 matches