213 replies to this topic

[daveCollins]

I WILL be 101 when I DO reach 50 years of observing ... got a late start. That's quite an accomplishment Jim.

[Castor]

[...]  Some of the guys laugh when I set up the tiny Takster which is about the size of a fetus, but I can tell you this much, I'll have a pretty good idea what I'm pointing it at and it's highly unlikely that whatever it is will look better in anything larger. Pick your mission and as with all things, everything is relative. Put aside your strong biases and check out some breathtaking showpiece doubles. For me, I love to see clean and crisp textbook images when I can. I'm happy to hear your impressions.

 

 

Took me forty years of aperture fever to discover that none of the bigger scopes that came along put up a more beautiful view of some objects than my 76 f/12. Daniel's post makes the power of small instruments very clear 

 

My aperture fever has been cured by the beauty of the views offered by small quality scopes. I now appreciate both more: the small AND big scopes. Enjoying each for what they do best.

I’m with Daniel and other posters here who prefer to watch double stars (and other suitable celestial objects) with small aperture refractors because most of the time I go out to observe for the aesthetics aspect and enjoyment that brings the contemplation of nature through a telescope and less for the challenge aspect, though I highly admire and respect those who do it for the challenge!

 

I second Erik's preference for small scopes precisely for the reasons that he wonderfully states in his post   and I no longer care for larger aperture scopes than what I already have, their frequency of use being almost inversely proportional to their aperture!

 

I should disclose that I observe from the city, so maybe I am biased for small scopes!  

Edited by Castor, 15 September 2018 - 10:42 PM.

[Jon Isaacs]

I’m with Daniel and other posters here who prefer to watch double stars (and other suitable celestial objects) with small aperture refractors because most of the time I go out to observe for the aesthetics aspect and enjoyment that brings the contemplation of nature through a telescope and less for the challenge aspect, though I highly admire and respect those who do it for the challenge!

 

I second Erik's preference for small scopes precisely for the reasons that he wonderfully states in his post   and I no longer care for larger aperture scopes than what I already have, their frequency of use being almost inversely proportional to their aperture!

 

I should disclose that I observe from the city, so maybe I am biased for small scopes!  

 

One variable here is seeing.  Small scopes can present a more aesthetically pleasing view when the seeing is on the less stable side of things but when the seeing is solid , the tight Airy disks a medium sized scope provides do have advantages aesthetically.  

 

My favorite double star scope is my 10 inch F/5 Dob.  It's a nice balance between aesthetically pleasing views and the capabilities a larger aperture provides.  It does takes some care and foresight,  collimation and cooling are critical.  But the views do make it worthwhile.  

  

 

I'm 70 this year and my eyes need all the help the can get.  The brighter,  tighter image a medium sized scope provides is a big help for me and is one reason i sold my 120 mm ED refractor . 

 

Anyway it's midnight , the moon set 40 minutes ago,  I woke up about 20 minutes ago.  The skies should be about 21.3 mpsas . The comet and some wonderful DSOs are waiting . Tonight its the NP-101 and the 16 inch with the eyepiece time approximately in the ratio of their apertures .

 

Wish me luck. 

 

Jon

[Erik Bakker]

Wishing you luck Jon 

 

Do use my biggest and smallest scopes with great pleasure. My favorite planetary scope is my 16" f/5. It just takes me there.

But on many a night, I observe with my 82mm ED with great joy and little effort. It gets used a lot.

[Castor]

Hi Jon,

 

I just came in from my backyard from a brief observing session with the TV-60 on a lightweight photo tripod and enjoyed looking at the Pleiades, Hyades and other bright clusters.  I just wanted to look at the Pleiades before going to bed because I was tired from work, but I stayed longer than expected because of the pleasing views and relaxing moments.

 

I didn’t even feel like taking the TV-76 scope out, so I’m glad that I got a smaller scope because otherwise I would not have done any observing at all!

 

Good luck and I wish that you have a productive observing night!  

Edited by Castor, 16 September 2018 - 02:37 AM.

[Jon Isaacs]

Hi Jon,

 

I just came in from my backyard from a brief observing session with the TV-60 on a lightweight photo tripod and enjoyed looking at the Pleiades, Hyades and other bright clusters.  I just wanted to look at the Pleiades before going to bed because I was tired from work, but I stayed longer than expected because of the pleasing views and relaxing moments.

 

I didn’t even feel like taking the TV-76 scope out, so I’m glad that I got a smaller scope because otherwise I would not have done any observing at all!

 

Good luck and I wish that you have a productive observing night!  

Thanks.  

I did have a good night. Found some new to me galaxies, saw a lot of old friends, the Horse head for one. It seems like it's one that slowly shows me more and more as the years go by.

The comet is moving about 2 degrees per night. Last week it was in the same field as M37 in Auriga, the night before last it was passing through M35.

I never did pull out tthe NP-101. Instead, towards the end of the evening I pulled out my 62mm F/5 Cometron achromat. Not quite a TeleVue 60.  There's something relaxing about viewing "easy targets" after hunting down 14the magnitude galaxies.

I spent quite a bit of time on M1, it was easy to find but not a lot different than those faint galaxies in the 16 inch, it took some effort to see anything.

And true to this thread and true to you, I gave Castor a shot with the Cometron.  Unfortunately, the optics in this scope qualify as marginal so an aesthetically pleasing view was not to be had. I could see the pair but the objective is a cemented doublet and seems misaligned and it was a rather nasty looking split.  Some years back I had a Parks 60 mm F/7 with a Carton objective that was quite good at doubles.

Daniel pointed out some of the aesthetic and other advantages to using smaller scopes for viewing double stars. I think it's worth adding that similar advantages exist when viewing the deep sky. Every dark sky moment does not need to be spent hunting down new and ever more difficult targets in a frenzy to get the most out every precious moment.

There needs to be time just to enjoy sweeping the Milky way in an 80 mm or hunting down M1 in a flawed 60 mm. 

One last observation: Optimizing the aesthetics of double star viewing. My rule of thumb is that the "best view" is very often with a scope that's double the Dawes limit. The double-double is about 2.3". The Dawes limit for a 50 mm. I think it really looks best in a 4 inch, 100mm. Of course for difficult unequal splits, more aperture maybe needed and beautiful splits can be made in smaller scopes. This a rule of thumb and we all know I have fat, clumsy thumbs.

 

(Not a double star killer)

 

jon

 

[figurate]

By coincidence, I was just casually ruminating on this several days ago with respect to applicability of the Nyquist theorem (in information theory) to optical resolution/contrast, and coming to exactly the same conclusion: in the same way that digital audio signals are sampled at twice the highest audible frequency for human perception, is there not an analogy here to a realistic limit for information extraction in a telescopic view, as Jon implied, of roughly double the theoretical limit? In other words, "connecting the dots" at a larger scale as opposed to separating the "dots", when splitting doubles at extreme magnifications, might actually require more resolution capability on the part of the instrument in order to represent useful information to our perceptual system. A signal-over-noise threshold, in other words.

 

And I am not speaking as an expert; it was just a passing thought, and this might actually be covered in the literature somewhere.             

[Jon Isaacs]

By coincidence, I was just casually ruminating on this several days ago with respect to applicability of the Nyquist theorem (in information theory) to optical resolution/contrast, and coming to exactly the same conclusion: in the same way that digital audio signals are sampled at twice the highest audible frequency for human perception, is there not an analogy here to a realistic limit for information extraction in a telescopic view, as Jon implied, of roughly double the theoretical limit? In other words, "connecting the dots" at a larger scale as opposed to separating the "dots", when splitting doubles at extreme magnifications, might actually require more resolution capability on the part of the instrument in order to represent useful information to our perceptual system. A signal-over-noise threshold, in other words.

 

And I am not speaking as an expert; it was just a passing thought, and this might actually be covered in the literature somewhere.             

 

To extract the high frequency data when sampled at the Nyquist frequency is not an easy task. Sharp cut off filters which add their own issues are necessary to avoid aliasing.  Near there Nyquist frequency the actual waveform must be extracted rather than simply reproduced. Oversampling is makes it much easier to capture the waveform.  I don't know what sampling rates studios use, I know 96 kilosampes/second is one standard.  In my research, I like to use 10x the sampling rate of the highest expected frequency.

The Nyquist frequency is more like the Dawes limit or the Rayleigh Criterion, an absolute limit on what can be resolved.

My 2x the Dawes limit or what I had previously mentioned 2X the Rayleigh Criterion is more like oversampling. At twice the Rayleigh Criterion, the first minima are matched so the Airy disks are clearly separated and the only loss of contrast are the overlapping diffraction rings.

Jon

[Castor]

 

Thanks.  

I did have a good night. Found some new to me galaxies, saw a lot of old friends, the Horse head for one. It seems like it's one that slowly shows me more and more as the years go by.

The comet is moving about 2 degrees per night. Last week it was in the same field as M37 in Auriga, the night before last it was passing through M35.

I never did pull out tthe NP-101. Instead, towards the end of the evening I pulled out my 62mm F/5 Cometron achromat. Not quite a TeleVue 60.  There's something relaxing about viewing "easy targets" after hunting down 14the magnitude galaxies.

I spent quite a bit of time on M1, it was easy to find but not a lot different than those faint galaxies in the 16 inch, it took some effort to see anything.

And true to this thread and true to you, I gave Castor a shot with the Cometron.  Unfortunately, the optics in this scope qualify as marginal so an aesthetically pleasing view was not to be had. I could see the pair but the objective is a cemented doublet and seems misaligned and it was a rather nasty looking split.  Some years back I had a Parks 60 mm F/7 with a Carton objective that was quite good at doubles.

Daniel pointed out some of the aesthetic and other advantages to using smaller scopes for viewing double stars. I think it's worth adding that similar advantages exist when viewing the deep sky. Every dark sky moment does not need to be spent hunting down new and ever more difficult targets in a frenzy to get the most out every precious moment.

There needs to be time just to enjoy sweeping the Milky way in an 80 mm or hunting down M1 in a flawed 60 mm. 
 

One last observation: Optimizing the aesthetics of double star viewing. My rule of thumb is that the "best view" is very often with a scope that's double the Dawes limit. The double-double is about 2.3". The Dawes limit for a 50 mm. I think it really looks best in a 4 inch, 100mm. Of course for difficult unequal splits, more aperture maybe needed and beautiful splits can be made in smaller scopes. This a rule of thumb and we all know I have fat, clumsy thumbs.

 

 

(Not a double star killer)

 

jon

 

 

Good morning Jon,

 

I’m glad that you had a good observing night, it would be a great one in my books   because after more than 30 years of observing I have never been able to conclusively see the Horse Head Nebula since I rarely travel to dark skies sites and when I do I usually bring my small scopes!

 

I know what you mean about observing “easy targets” with your 62mm Cometron because my first grab-n-go scope was a NexStar 80mm f/5 achro that was great for looking bright DSO’s and rich-field viewing but very poor for the planets and double stars!

 

Even if we have diametrically opposed observing conditions and different objectives and priorities we share the concept to use the right tool for the job!

 

I always learn from your posts -thank you!  

[Jon Isaacs]

Castor:

 

This Cometron makes a Celestron ST-80 seem like a TeleVue . My Celestron ST-80 splits Castor with ease and even does a decent job on the double-double .

 

If you ever get out this way. . We could hook up and you could see the Horsehead . 

 

Jon

[Oz Alfert]

 

gosh . . .  how I love this hobby and community

[25585]

Is "pop a cap" a new observing expression?

 

Owning 3 100mm fracs, F5, F9 and F14, that size is definitely the most useful, whatever focal length.

 

I want a TV85 someday though. Only prevarication on colour choice, or whether a 76 would lose much in comparison,  has got in the way. 80 to 90 though have that special slot between most big affordable binocular models, and 4 inch refractors. Good for astro and terrestial.

 

Star separation to me is more having the brighter ones not bright enough to dazzle-out fainter stars. For Sirius B, I have not managed it below 100mm, as too faint otherwise. Several things have to be just right. 

 

I too think the Burnham books are wonderful. Wish they were on Kindle. The now much ignored Sky Catalogue 2000.00 Vol.2 is also good in conjuction with Sky Atlas 2000.00. Yes I use big old setting circles too. GOTO is swinging manually go RA and Dec on printed co-ordinates.

 

Celestron's C9 MCT is good for double stars, in fact it's a great small do-all. No not a refractor, but it does have a glass lens up front.     

 , 

Edited by 25585, 16 September 2018 - 04:03 PM.

[Sasa]

As someone who has used telescopes with apertures as small as 50mm on a regular basis and down to 10mm as an experiment, I can't agree more with the OP.

But I would also like to point out that small telescopes can actually reveal quite a bit of deep-sky objects, even under less than perfect dark skies. My local weather has become quite erratic and clear nights are not as common as they used to be and I often have to take advantage of very short periods of clear skies. This strongly favors small telescopes and simplified setups, which means I've used my 63mm Zeiss a lot more lately than my 12" dobsonian and I've often observed deep-sky in twilight or moonlight, despite having quite dark skies, simply because I couldn't afford to waste what little observing time that bought me instead of waiting for a better opportunity that might be weeks away.

What I have discovered is that even under a mag 3.5 - 4.5 sky, meaning one where the Milky Way in Cygnus, high overhead, is not visible or just coming into view, even a 60mm allows surprisingly good views of a frankly startling number of objects, provided that you know what you're doing. And if you're living under severely light polluted skies in a major urban center, taking a 60mm to a mag 4 sky can be orders of magnitude easier than taking a 12" to a mag 6 sky. It can mean the difference between an easy half-hour drive and a multiple-hour expedition. Of course it's fun to go to really dark skies, but if it takes four or five hours to do, it's not something you do on a normal evening when you have to get up at five the next morning to go to work.

Obviously, observing deep-sky under such conditions with such a small telescope takes a completely different mindset than observing under dark skies with a 12". A lot of objects that are easy in a 12" will be a challenge merely to detect, but that in itself is fantastic workout and training for when the clear, moonless weekend finally arrives and you can take the 12" out to the state park natural reservation and observe all night for two nights.

I know this is old hat to a lot of people, but I also frequently encounter people that seem not to be aware of how much is possible under less than ideal conditions, if you give it a serious go. And lots of people everywhere seems to just automatically dismiss the idea that small scopes can show anything worthwhile at all. A small scope under bright skies? A waste or time, surely. Wrong! Nothing could be further from the truth.


Clear skies!
Thomas, Denmark

This is what I do most of the time - I do a lot of DSO observing from our light polluted backyard with small refractors. Here is an example, documenting what Daniel was saying. During observation of NGC663 I noticed some nearby orange and blue stars. These are of magnitude 8.0 and below. I was quite surprised that I can see colors for such faint stars in 60mm:

Edited by Sasa, 17 September 2018 - 09:16 AM.

[Defenderslideguitar]

Wow  great thread    great read     and what an education for the fairly inexperienced (me).

While I am not ever going to stop using the 4 inch  refractors I like,  especially on planets... It is nice to see that the 60-76-80mm refractors arent just for quick grab and go sessions . I  like the 3 inch refractors for easy set up and use and travel...nice to see them get recognition for other things

[Mike W]

Wow  great thread    great read     and what an education for the fairly inexperienced (me).

While I am not ever going to stop using the 4 inch  refractors I like,  especially on planets... It is nice to see that the 60-76-80mm refractors arent just for quick grab and go sessions . I  like the 3 inch refractors for easy set up and use and travel...nice to see them get recognition for other things

 

Speaking of 80mm refractors how's that Selsi you got from me?

Mike

[Castor]

Castor:

 

This Cometron makes a Celestron ST-80 seem like a TeleVue . My Celestron ST-80 splits Castor with ease and even does a decent job on the double-double .

 

If you ever get out this way. . We could hook up and you could see the Horsehead . 

 

Jon

 

That bad?    My NexStar80 probably suffered from spherical aberration besides the usual CA and it made high magnification use a frustrating exercise, but I was still happy with it because it allowed me to participate in local star parties instead of staying at home with the 10-inch SCT under light polluted skies!

 

Thanks for the invitation, you are very kind!   Unfortunately I am far from you and I rarely ever travel, but I have been in the California and Nevada deserts and the skies over there are amazingly dark and clear, you are very lucky!

 

Best,

[Brent]

 

 

I too think the Burnham books are wonderful. Wish they were on Kindle. 

I got them on Kindle years ago.  'Just checked, and they are still there.

 

Brent

[Defenderslideguitar]

Speaking of 80mm refractors how's that Selsi you got from me?

Mike

Mike  well I love the Selsi. I like that it has great views and plays well with all my favorite mounts since you set it up with rings and vixen bar. It rides well on both the Vixen GP 2 mount and the twilight alt az. The fact that it is already set up for 1.25 eyepieces helps this novice so much.  Although I have several 75-80 mm scopes, the Selsi is the go to 80mm. I took it to Block Island, R.I.  I took it to Maine but mostly I  take it out all then time at home       a true test for any scope  .. a keeper...Thanks

Barry

Edited by Defenderslideguitar, 16 September 2018 - 09:50 PM.

[rolo]

I gotta pop a cap in this thing once and for all. In-light of this recent thread https://www.cloudyni...ral-refractors/ I decided to do this "visual" experiment over the course of the past couple of nights with a few of my observing buddies, DarrenT, David Person and mikona who are also members here on CN. I wanted to gather their opinions to see if they agreed or not and overwhelmingly they were blown away at the results. This is very common knowledge among many seasoned double star observers, yet there's still an astonishing amount of experienced observers who are still under the impression that larger aperture is literally "always" better and that concept just blows me away. I have noticed that whenever I discuss this in the double star forum, many observers understand it and really get it, yet whenever I post this in the refractors forum, It's almost always met with skepticism.

 

To me there are many myths in astronomy like, how important it is to have dark skies, yet 80% of where I enjoy my observing is in light polluted skies. For example, Alvin Huey and Don Pensack love to observe faint fuzzies and I totally get that. If I was into faint fuzzies more, I'd use a big Dob and find the darkest skies possible to see them. We all know that term "clear skies". Read any of my posts and you will rarely ever see me write "clear skies". My signatures almost always read "steady skies" because most of what I care about is steady air. I absolutely despise bad seeing with a passion. I'll take light pollution just fine, but I absolutely dread bad seeing because everything I love to observe relies heavily on steady skies. Just recently, I was viewing double stars in a really dark sky. At higher magnifications, I actually found it slightly annoying because it makes it harder to frame carbon stars and double stars in the center of the FOV because I can hardly see the field-stop of the eyepiece which I use to frame stars. I totally get it if others want their dark skies, but they're really not needed for everything observers look at and I think there's still a countless number of observers who still don't really quite understand this concept. I often keep ambient lights around me in the yard which are kept on constantly while I'm observing the solar system, Moon and certain stars and that's how I prefer it for several reasons which I've shared in other threads. There are some advantages to these methods and some disadvantages. I know that's hard for countless observers to believe, but it's true.

 

But, let's get back to those useless smaller apertures so many others are convinced of. Have a look here. How could anyone use a petty 3" telescope? It's not big enough you say, but that's just really bad information when someone gives you that impression. If anything, it merely reflects their own lack of personal experience on what a small lens is actually capable of showing them.

 

https://www.cloudyni...telescope-r1874

 

So, let me put this in bold letters so it's actually more clear. There are many instances where increased aperture is actually a hindrance to images. I have a 60mm, 90mm, 102mm, 128mm, 152mm, 250mm. There are countless targets the smaller 60mm refractor will literally and clearly outperform all of the larger apertures. I've sometimes asked myself why Burnham's Celestial Handbook has been such a goldmine to me over these past 25 years and I've come to realize it's because Burnham gave so much attention to individual stars. Robert Burnham Jr. was a 20th century jewel. It's a companion with lists that read like this....

 

1.) LIST OF DOUBLE AND MULTIPLE STARS
2.) LIST OF VARIABLE STARS
3.) LIST OF STAR CLUSTERS, NEBULA, AND GALAXIES

 

When I read deeper into that, some interesting thoughts come to mind. The first thing is that I can observe categories 1 and 2 from the convenience of my light polluted skies perfectly fine. The only time light pollution is of a hindrance is if the targets are too faint, but don't forget, there are countless targets that are not too faint or unresolvable in smaller apertures which can be studied and observed. Still, many insist that astronomy isn't enjoyable unless it's under dark skies. For the vast majority of beginners who are primarily looking at showpiece objects like M13 and M31, of course darker skies help, but you have to remember that observational astronomy is not always about deep sky targets like those listed in category 3.

 

The late great Leslie Peltier who wrote "Starlight Nights" observed over 100,000 variable stars said this about his 6" and 12" achromatic refractors. "Each telescope has its own particular sphere of usefulness. Each one can perform its own specific duties much better than could the other one, so there is really no cause for any rivalry between the two and I, for my part, have always done my best to insure domestic tranquility by alotting them equal observing time". Those were the words of a very wise and extremely experienced observer, so if anyone tells you aperture is a must, ask them if they've ever observed 100,000 variable stars before.

 

Okay, so let's get back to this aperture thing, shall we? You have a few options. You can take one large refractor and use a couple of different aperture masks as if you had several refractors of different aperture, or if you don't feel like lugging out a big scope and masking it down, then set up a 60mm achromatic or ED lens or a portable 80mm lens. I assure you, you will have a blast if you know what you're doing. The problem is many observers don't understand what targets look best in certain apertures because they're probably just into deep sky showpiece objects and are not familiar with this. The other problem is knowing the limits of your telescope and this is also where the problems stem from. Another issue is countless observers have the incorrect perception that every double or multiple star you want to see has to be the tightest double. Ahhhhhh..... I gotta have a telescope that splits the tightest doubles obtainable and that means its a better telescope for doubles. If you think that, then you're missing the boat. Let's just do some basic stuff. We'll just use the common Dawes limit. 4.56 divided by your aperture in inches.

 

2" aperture 2.2"
5" aperture .9"

 

Okay, set your parameters for your 2" telescope. Select doubles that are about 3 arc seconds or more. Just select doubles that are above or close to the Dawes limit of any aperture. Also, for a 2" or 3" glass, select brighter doubles like 0 to 8th magnitude that are typically your showpiece doubles. I used my FS128 which comes with a dust cap that has about a 2" aperture opening that simply unscrews from the center of the cap. The target chosen for this demonstration was Alpha Hercules "Rasalgethi". Here's some info on this double. We looked at about two dozen showpiece objects but I'm just using this one for explaining this. There are many more.

 

http://www.perezmedi...ves/001394.html

http://stars.astro.i...rasalgethi.html

 

For this comparison we used 104x and 173x with a 10mm and 6mm Ortho and my 1.25" Tak prism diagonal. Seeing looked pretty good but not great because we were in the valley. At 128mm full aperture, Rasalgethi appeared like the images you see here in Pickering 4 and 5. The two stars also looked a bit over exposed, so the colors did not appear as distinct as we would have desired or have seen in the past. In other words, they were slightly washed out from the seeing. The separation and magnitude of these two stars is also within the grasp of each aperture. I then placed the small mask over and the differences were incredible to say the least. Several things changed and I let the guys decide what they liked after we all compared the two images.

1.) With the 2" aperture applied, the airy disks looked larger and clearly more distinct due to the decrease in resolving power. At 5" aperture, the airy disks appeared smaller, brighter, noisier like Pickering 4 and less colorful.

2.)  At 2" aperture, all the scintillating was clearly reduced. The brighter component looked like Pickering 8 and 9 while the secondary component looked like Pickering 10 in fact we could only see a very slight diffraction ring around the primary while the secondary was nonexistent altogether. In other words, just two textbook pinballs that looked absolutely breathtaking.
3.) All of us overwhelmingly agreed the colors were clearly more obvious and distinct in the smaller 2" aperture and less over exposed looking like they were at 5".
4.) mikona was especially in awe at this because he was not aware that this is what happens when you reduce aperture for many double stars. mikona also has a SkyWatcher 120ED and when I came over to explain what we were doing, he realized that his telescope also has about the same size aperture opening which can easily be removed from the front dust cap. He later also swung over to Mizar and Alcor with the 2" aperture and dropped his jaw in disbelief at how beautiful and perfectly textbook the images looked.

 

This then taunts the next question. Many observers will swear stars are more colorful in larger apertures but that's not the only way works. There's a big difference between stars and extended objects like planets and planetary nebula for example. Certainly in those cases, the larger apertures will usually provide you with increased color contrast, but stars are another story. These points of light can often easily appear washed out or over exposed looking in appearance while reducing aperture increases and exposes the airy disk. This in turn makes the stars appear almost immune to some seeing conditions compared to larger apertures. The result is that you can see solid distinct disks with colors displayed more easily. This taunts another question still. Many observers will say that seeing affects apertures the same way. My suggestion is to cut yourself a cardboard aperture mask 80mm to 60mm from a cereal box and see for yourself and you be the judge. I hope others aren't stuck in bad weather, otherwise I'll probably never hear the end of their stat sheets.

 

Some of the guys laugh when I set up the tiny Takster which is about the size of a fetus, but I can tell you this much, I'll have a pretty good idea what I'm pointing it at and it's highly unlikely that whatever it is will look better in anything larger. Pick your mission and as with all things, everything is relative. Put aside your strong biases and check out some breathtaking showpiece doubles. For me, I love to see clean and crisp textbook images when I can. I'm happy to hear your impressions.

Daniel,I've done this same test a few times and I completely agree. But, by same token there are many doubles that look like elongated blobs in a smaller apertures that are cleanly split in a larger instrument.That's what I get off on. My favorite aspect of double star viewing is splitting tight even sub-arc second doubles that samller scopesjust can't split. I find this type of extreme double star observing the most challanging and most rewarding(personally). Yes, I enjoy asthetically pleasing doubles in smaller scopes and enjoy the pretty text book airy disc as well but anyone can split those doubles. Even with smaller scopes I like to take them to their double star "red line". With my C14 (under steady seeing) I have cleanly split sub-arc doubles at 568x with a 7mm ortho that an excellent 8"f/8 Newtonian coudn't split. No it wasn't a pretty split but a split nonetheless. With my old 12.5" f/6 Cave You could drive a truck through each component of Epsilon Lyrae at 952x with 4mm Ortho and 2x Barlow.

 

As far as more colorful I find the my AP180  shows tighter more pinpoint and more a vivid variation of colors in many open clusters tha the the FS128 and far more than the FS102 or TV102 could. For example the double cluster which is a dream to observe in large APO with 31mm Nag or 41mm Pan.

 

Like you said above "This is very common knowledge".  Maybe I'll right an article on the benefits of large APO's for sub-arc second double star splitting.You know, I can always mask a larger scope but I can never increase the aperture of a smaller one. So, the larger scope is a win win in my book.

 

Don't get me wrong here, I've had over 200 scopes and loved them all(except a few lemons). I love my little FC 50 and TV102 along many others like the Vixen 70mm,80mm and 102mm Fluorites.I loved my Unitron 152, a 4" f/15 beauty that was double star beast! But at the end of the day I'll take the AP180 all the way to the grave! For me the bigger the better. Too much horsepower? Let off the gas! Too little horsepower and fall behind!

 

 

 

 

By the way I encourage double star observers to join the Astronomical Leage's double star observing program and get an award when completed!

 

Here's  list of doubles in the Astronomical League Observing program which is well suited for scopes as small as 80mm.

 

I told you we would be doing this again

 

I have nothing but mad respect for you  I apprecaite your time and effort to educate us with your knowledge and experience.

 

PS Please lose the "Pop a Cap" phrase.

Edited by rolo, 17 September 2018 - 06:34 AM.

[Ballyhoo]

I was also going to comment, that open clusters can do quite well with 4" refactors in suburban orange zones - perhaps 80 mm  as well.

But can someone explain the draw of variables?  I would like to appreciate the objects but not sure I understand the allure. The periods of variability are always much greater than a single observing session,no? 

 

Daniel, your post is wonderful at explaining why smaller aperture instruments are so well suited for double stars, also for those of us that have not yet appreciated those objects, can you explain your allure (or others posters here) to binaries? I mean, OK, Albireo is a pretty target, and  Mizar is instresting, but for a few moments. I dare say though, if I am not appreciating something, it is prob bc I do not understand or know  what to look for. I will qualify this statement with that opening up and reading Burnham can be the antidote for ignorance. He  usually makes any single object completely unique and interesting.  Plus he wrote the book at a time just preceding the explosion of larger aperture instruments into the amateur market.

[Ed D]

OK, so it's not just me that finds the colors of Albireo and other colorful stars best when I observe through my 60mm f/15 achro.

 

One neat 'challenge' I find with observing using smaller apertures is that on multiple stars it sometimes takes careful selection of eyepiece magnification/exit pupil to be able to see some of the dimmer stars.

 

Small scopes aren't solely for grab-and-go convenience.  They are a lot of fun and fill a niche in our observing arsenals.  Thank you, Daniel.

 

Ed D

[Mr Onions]

I regularly use  50mm and 40mm stops from inside looking through double glazing { don't get sciatica } it really tightens up the image.

 

Yesterday I used a WOZS66 with a 40mm stop over dew shield and used a TV Nagler 3-6mm zoom at the 3mm setting, to view a small plaque, located about 300 yds away along a straight road.

The magnification was 130X { approx } and the 40mm stop really sharpened up the image when I compared it to the full 66mm.

Of course it was a dimmer image as the objective lost a full inch of aperture but it was a much tighter and hence a far more pleasing view.

 

I well remember my 2nd thought when I took my first look through an Oracle 3 { after waiting 6 weeks for a clear night! } it was, "Wouldn't it be great it Tele Vue made a 45mm version"

My first thought was, incredulity at just how good this view was compared to department store scopes, which was all I had been used to.

[BillP]

OK, so it's not just me that finds the colors of Albireo and other colorful stars best when I observe through my 60mm f/15 achro.

 

Nope...not just you.  For many of the showcase colorful doubles the colors are much more vividly portrayed to my eye by the smaller apertures instead of the larger ones.  The larger apertures tend to wash out the colors a bit by comparison.  Larger apertures will of course show the colors on dimmer stars better though IME, but the brighter stars are more fun to observe for me.

[Astrojensen]

But can someone explain the draw of variables?  I would like to appreciate the objects but not sure I understand the allure. The periods of variability are always much greater than a single observing session,no? 

There are many variables that change noticeably on a MUCH shorter timescale. Some, most notably short-period eclipsing binary stars, can change in an hour or even less. If you are extremely lucky, you could also see a flare on a nearby M or R-class red dwarf and see it rise five to ten magnitudes in a few minutes! You had better be extremely lucky, though, but it has happened. See Burnham's for details. I'll let you find the chapter yourself.    

 

But many variables only change slowly, of course. That doesn't mean that they are uninteresting, though. Especially the irregular ones can be interesting, because you never quite know what they're up to. Following variables during years and decades can make them become like old family or a pet. 

 

 

Clear skies!
Thomas, Denmark

[Astrojensen]

Daniel, your post is wonderful at explaining why smaller aperture instruments are so well suited for double stars, also for those of us that have not yet appreciated those objects, can you explain your allure (or others posters here) to binaries? I mean, OK, Albireo is a pretty target, and  Mizar is instresting, but for a few moments. I dare say though, if I am not appreciating something, it is prob bc I do not understand or know  what to look for. I will qualify this statement with that opening up and reading Burnham can be the antidote for ignorance. He  usually makes any single object completely unique and interesting.  Plus he wrote the book at a time just preceding the explosion of larger aperture instruments into the amateur market.

For me, most double stars are pretty, but not all that exciting. For me, the exciting and interesting ones are those that are hard to see in the telescope I'm using at the moment. I've always liked to see hard and difficult objects, simply because of the challenge, and doubles can present extreme challenges that doesn't require dark skies to observe, but require extremely good seeing instead. The better the scope, the more you can push it to the limits and if you're really skilled and your scope unusually good, you can often go beyond what is normally considered the limits of the aperture. Objectively speaking, it is of course nothing more than pointless bragging, but it makes oh so much fun to do!   Hunting for difficult doubles, merely for the sake of seeing them, has lots in common with catch and release fishing and look how popular that hobby is.  Both obviously involves a great deal of honesty, especially in double star hunting, because we obviously can't simply show a selfie of ourself with Izar in our lap, caught with a 30mm achromat in the backyard. 

 

 

Clear skies!
Thomas, Denmark