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Nothing to see, but loads to see....


Stu
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37 minutes ago, jetstream said:

Buy one IMHO.

Used one for years and are considered the best out there. Your 100mm Triplet will give extremely good views. I've found that going up to 120mm makes observing much more seeing sensitive. My 90mm is much more flexible in regards to this. That being said, when conditions allow, the extra aperture really makes a difference.

You might be shocked at the views with your scope and a Baader Cool Wedge.

You're making it very difficult for me to keep my wallet closed! I am on the lookout for one.

thanks for the info.

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13 minutes ago, Sunshine said:

You're making it very difficult for me to keep my wallet closed! I am on the lookout for one.

thanks for the info.

You check out Alpine Astro? very good to deal with

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15 hours ago, Nigella Bryant said:

I really love white light solar observations too. Nothing wrong with that. Granulation is fantastic to observe as well as the changes in spot development over day's. Images taken with just an 80mm ed refractor and Lunt wedge with zwo ASI 178mm camera. What's not to like. 

20200706-092716UTellabryant-AR2835-WL-col.jpg

20200706-093139UT-UnnamedAR-WL-1-1 -col.jpg

20210630-100207UTellabryant-WL-AR-col.jpg

20210630-100207UTellabryant-WL-AR-1.jpg

These images have stirred me, I am searching for a wedge!

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2 minutes ago, Sunshine said:

These images have stirred me, I am searching for a wedge!

Btw, it takes the very best images to equal what the eye sees on solar. Solar views through nice optics is stunningly good. Gonna go check GONG out now myself to see whats happening. Crystal clear skies atm.

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2 minutes ago, jetstream said:

Btw, it takes the very best images to equal what the eye sees on solar. Solar views through nice optics is stunningly good. Gonna go check GONG out now myself to see whats happening. Crystal clear skies atm.

Good to know, I have had H-alpha scopes in the past but on both occasions stupidly sold them on impulse to fund other items, I cannot emphasize the word "stupidly" enough. In the coming year or two I will have another but

for now I really would really like to try out a good wedge with my scope.

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I have a reasonably good working Quark that I might dig out now that it has warmed up and the sun is getting more active. I still think the PST is a nice unit to have around and might pick one up.

1 minute ago, Sunshine said:

or now I really would really like to try out a good wedge with my scope.

By all means- you have the optics to maximize the views.

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My best ever white light views have been with the Tecnosky 125 APO and Lacerta wedge. Used to have a Baader Cool Wedge but used on a smaller scope and while it gave good views my latest setup is better. Think the combination of wedge and scope is the key. 

Also used the Lacerta on an Orion 120mm f/5 (same as SW) and wasn’t that impressed.

Edited by johninderby
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14 minutes ago, jetstream said:

I have a reasonably good working Quark that I might dig out now that it has warmed up and the sun is getting more active. I still think the PST is a nice unit to have around and might pick one up.

By all means- you have the optics to maximize the views.

Yes I feel my scope would make a good pairing with a baader wedge in good seeing.

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I bought an Altair wedge just before winter, and it's only been used once!  That's primarily because of the weather actually, which is the same reason I haven't used my Daystar Quark for 3 months or more, up until the Sunday just gone!  I have an ES 102mm AR102 which I bought specifically for h-alpha viewing, but I found the CA a bit off-putting when using white-light. 

I bought a 102mm f/11 Altair Starwave just yesterday.  It's been slightly shortened, and it only cost £120!  Was thinking I might try some side-by-side white light and h-alpha, as it's mounted on an AZ-EQ6 GT.  I was hoping it might be shortened enough to binoview without the corrector, but not quite :)

I would like to try white light some more.  I think the CA was bad enough on the AR102 (f/6.66) that it smooshed any granulation detail.  Not sure.  This f/11 scope will reduce the CA significantly, I'm hoping, and get me in closer! 

Of course, I could try a Baader film on the 10" newtonian pictured too!

I'm going to try the OIII filter, in lieu of a continuum filter.

altairr_starwave_102mm_f11.thumb.jpg.8641b8adb871ae98426cae3bdb814ec9.jpg

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27 minutes ago, tombardier said:

I bought an Altair wedge just before winter, and it's only been used once!  That's primarily because of the weather actually, which is the same reason I haven't used my Daystar Quark for 3 months or more, up until the Sunday just gone!  I have an ES 102mm AR102 which I bought specifically for h-alpha viewing, but I found the CA a bit off-putting when using white-light. 

I bought a 102mm f/11 Altair Starwave just yesterday.  It's been slightly shortened, and it only cost £120!  Was thinking I might try some side-by-side white light and h-alpha, as it's mounted on an AZ-EQ6 GT.  I was hoping it might be shortened enough to binoview without the corrector, but not quite :)

I would like to try white light some more.  I think the CA was bad enough on the AR102 (f/6.66) that it smooshed any granulation detail.  Not sure.  This f/11 scope will reduce the CA significantly, I'm hoping, and get me in closer! 

Of course, I could try a Baader film on the 10" newtonian pictured too!

I'm going to try the OIII filter, in lieu of a continuum filter.

altairr_starwave_102mm_f11.thumb.jpg.8641b8adb871ae98426cae3bdb814ec9.jpg

Beat of luck! I’m sure the Starwave at f11 will make a positive impact on the CA, curious about your result with it once you have a peek.

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25 minutes ago, Sunshine said:

Beat of luck! I’m sure the Starwave at f11 will make a positive impact on the CA, curious about your result with it once you have a peek.

I'll report back!  I'm looking forward to trying it on the moon too.  I want to see what all this 'contrast' people keep on going on about looks like (compared with my reflector).

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This may be a daft question but when using a refractor and a cool wedge is there any issues which could arise considering the amount of heat the scope is subjected to? heating of the lens cell or focuser for example. As I understand the wedge dissipates the heat but there must be a substantial increase in heat within the optical tube, is it advised to keep observing to a limited time and allow the scope to cool? or am I being paranoid.

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Just now, Sunshine said:

This may be a daft question but when using a refractor and a cool wedge is there any issues which could arise considering the amount of heat the scope is subjected to? heating of the lens cell or focuser for example. As I understand the wedge dissipates the heat but there must be a substantial increase in heat within the optical tube, is it advised to keep observing to a limited time and allow the scope to cool? or am I being paranoid.

The heat is concentrated where it's focused.  At the objective, where the rays are parallel, it's not too dissimilar from sun coming through the window in your house.  That's the way I understand it anyway!

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1 hour ago, tombardier said:

I bought an Altair wedge just before winter, and it's only been used once!  That's primarily because of the weather actually, which is the same reason I haven't used my Daystar Quark for 3 months or more, up until the Sunday just gone!  I have an ES 102mm AR102 which I bought specifically for h-alpha viewing, but I found the CA a bit off-putting when using white-light. 

I bought a 102mm f/11 Altair Starwave just yesterday.  It's been slightly shortened, and it only cost £120!  Was thinking I might try some side-by-side white light and h-alpha, as it's mounted on an AZ-EQ6 GT.  I was hoping it might be shortened enough to binoview without the corrector, but not quite :)

I would like to try white light some more.  I think the CA was bad enough on the AR102 (f/6.66) that it smooshed any granulation detail.  Not sure.  This f/11 scope will reduce the CA significantly, I'm hoping, and get me in closer! 

Of course, I could try a Baader film on the 10" newtonian pictured too!

I'm going to try the OIII filter, in lieu of a continuum filter.

altairr_starwave_102mm_f11.thumb.jpg.8641b8adb871ae98426cae3bdb814ec9.jpg

It is as much Spherical Abberation as Chromatic Abberation that kills the granulation detail. Fast achros are not ideal for solar white light as they often suffer from SA so either a long focal length achro like the 102mm f11 or a decent apo doublet like the ED100 or an f7 such can be found around these days for reasonable prices would be a good choice for better detail.

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35 minutes ago, Stu said:

It is as much Spherical Abberation as Chromatic Abberation that kills the granulation detail. Fast achros are not ideal for solar white light as they often suffer from SA so either a long focal length achro like the 102mm f11 or a decent apo doublet like the ED100 or an f7 such can be found around these days for reasonable prices would be a good choice for better detail.

Using low mag eyepieces on the 102mm f/6.66 does show large amounts of distortion at the edges.  I've not been sure whether that's SA, or pin-cusion distortion, or what!  I've not really used it for any astronomy, just with the Daystar Quark.  I've got a TSO f/7 ED doublet too, which has quite nice colour correction when lunar viewing (blue star bloat if you try imaging with it though).  I bought that for Ha viewing too.

It looks like I'm going to be waiting 4-5 days to try out this f/11, which is really annoying!

Anyway, once I've figured out what's good for what, I'll be thinning down the herd of telescopes.  Too much overlap between the 3 refractors, and too much overlap on my 200P and 250P too.  I do need to try a maksutov at some point :)

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Well SGLers I just got in from a nice solar viewing session :D

It was cold in the seacan and it took awhile for the optics to come around. Once settled in the 90mm APO/Coolwedge gave some great views in avg to good seeing, influenced by some wind. Nice granulation around the larger sunspots- no cell structure though, seeing not stable enough. Many little "mini" sunspots about this area.

Over to the other side the 2 sunspots sported some nice faculae in the area - great to see again.

Took a while for my eyes to turn the green to yellow in my wedge and also remembered the importance of either a zoom or many eyepieces. The ability to change mag today was of major importance in the changing conditions. The Baader Coolwedge just plain old works in all 3 of my fracs, an excellent piece of equipment.

Great to obs solar again and I hope the suns activity continues to increase.

 

IMG_E1764.JPG

Edited by jetstream
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2 hours ago, tombardier said:

Using low mag eyepieces on the 102mm f/6.66 does show large amounts of distortion at the edges.  I've not been sure whether that's SA, or pin-cusion distortion, or what!  I've not really used it for any astronomy, just with the Daystar Quark.  I've got a TSO f/7 ED doublet too, which has quite nice colour correction when lunar viewing (blue star bloat if you try imaging with it though).  I bought that for Ha viewing too.

It looks like I'm going to be waiting 4-5 days to try out this f/11, which is really annoying!

Anyway, once I've figured out what's good for what, I'll be thinning down the herd of telescopes.  Too much overlap between the 3 refractors, and too much overlap on my 200P and 250P too.  I do need to try a maksutov at some point :)

Spherical aberration is different to geometric distortions. It is where light from different parts of the lens does it all focus at the same place, explanation here. It does kill off fine detail, so I would never recommend a fast achro for white light solar, although some perform better than others.

https://en.m.wikipedia.org/wiki/Spherical_aberration
 

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1 hour ago, jetstream said:

Well SGLers I just got in from a nice solar viewing session :D

It was cold in the seacan and it took awhile for the optics to come around. Once settled in the 90mm APO/Coolwedge gave some great views in avg to good seeing, influenced by some wind. Nice granulation around the larger sunspots- no cell structure though, seeing not stable enough. Many little "mini" sunspots about this area.

Over to the other side the 2 sunspots sported some nice faculae in the area - great to see again.

Took a while for my eyes to turn the green to yellow in my wedge and also remembered the importance of either a zoom or many eyepieces. The ability to change mag today was of major importance in the changing conditions. The Baader Coolwedge just plain old works in all 3 of my fracs, an excellent piece of equipment.

Great to obs solar again and I hope the suns activity continues to increase.

 

IMG_E1764.JPG

Looks fabulous Gerry, but cold! 🥶🥶

The Sun is definitely getting more active, so it’s worth keeping an eye on now, seems to be at least something to see everyday now.

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Great post, there's years of experience behind that commentary and it's something anyone interested in solar observing would benefit from reading.

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On 02/03/2022 at 13:32, Stu said:

🤣🤣. Well, I always thought the problem was that the heat was more concentrated at that point so you risked the secondary overheating, coming unglued etc. clearly not a problem on your scope 👍

I re-read this, I didn't mean to sound 'off'. You have prompted me to go and measure it now, on the next sunny day!. 

There's no glue on this scope to melt so that potential problem hadn't crossed my mind.  

Trying to do some physics I think it goes like this : 

The primary is 150mm and the secondary is 72mm in diameter, but reflects 85%s so I make that about 2.75W from solar collected by the scope ( primary shaded by secondary ) and 2.75  from direct solar heating to the surface of the secondary facing the sun, the lack of difference being due to the shading effect of the primary vs the lower reflectance of the front of the secondary. 

The equilibrium temperature will be the temperature at which the object ( the secondary mirror unit) will radiate the same amount of energy it receives. 

ie using Stefan-Boltzmann, P = σAT^4 where sigma = Stefan-Boltzmann constant σ = 5.670374419...×10−8 W⋅m−2⋅K−4.[5]

So T = ( P/sigma.A)^(-4) which is ... 330K   or 57 Celsius

Using W = 1350 W/m^2 as the solar irradiance, 150mm as the diameter of the primary, 72mm as the diameter of the secondary, 85% as the reflectivity of the aluminised surface and 50% as the reflectivity of the surface facing the sun. 

If I repeat this for an OG of 100m diameter I get

input power into the glass = 1350* PI* 50mm^2*0.045 = 0.5W

where the transmissivity of BK7 glass is 95.5% so the absorptivity is 4.5%

Which means the equilibrium temperature turns out to be .. 153K . or roughly -120C

Well, nice to see its a chilly sunny day for the refractor users!

Anyone see where I went wrong ? 

 

 

 

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