| Best focal length | |
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| < 20 mm | |
| 20 - 70 | |
| 70 - 135 | |
| 135 - 250 | |
| 250 - 500 | |
| 500 - 800 | |
| 800 - 1200 | |
| > 1200 mm | |
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3.81
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Just out of curiosity what is your favorite focal length and if you like pls tell why. |
3.61
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| Mine has more to do with optics than focal length. I really love my esprit120. I use it at both 650 and 850 focal lengths. Really happy with that field of view on most nebulae (with my 2600mm) but more importantly the stars are the sharpest in my arsenal. |
7.90
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Andi: Why would you think it is important? I don't have any nor one is preferred to any other since subject and circumstances are the determinant factors of focal length choice. |
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3.81
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andrea tasselli:Andi: I don’t. It isn’t important at all. I am just curious what people like the most. |
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7.90
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Andi: Never thought people would have a "preferred" focal length (unless is simply the one they have) but let's what comes out, it would be interesting... |
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andrea tasselli:Andi: Guess my question is equally useless, as to ask what your favorite watch or car brand is and still i find it interesting. especially because i am interested in the reasons why. Do you like shorter focal lengths because you can be mobile, do you like longer ones because you have more to photograph etc. for me personally it is the 500-800mm range. It seems to be the range of the dedicated amateur astronomer, so i find a lot of work here on astrobin which i can look at and try to image myself. It also looks like that is a focal length where you can get more or less affordable scopes with a good quality. |
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7.90
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| If I were to chose purely on efficiency reasons and rejecting in principle most large emission nebulae I'd go for a long focal length (2 mt and above), if I had the seeing to support it as well as the time (and the darkness of the sky to go with it). As it is, 1200-1400 mm would be as much as I can or could potentially afford (money matters). |
1.20
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Andi: ~900mm with 3.76um pixel size. It's something I can guide every night yet it produces the best framing for targets I'm interested in. |
0.00
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| I have no special focus lengths. So I own two telescopes with FL 550mm and 980mm. For me this has to be suitable to the objects I like to take photos from. And even in visual astronomy I like the medium scopes, because I can use smaller eyepieces than with bigger scopes. |
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I don't really have a favorite focal length either, I have three tubes, one 350 mm, one 580 mm and the last one I'm working with now which is 1000 mm and I think each tube is good depending on the object you're photographing. However, if economy allowed me to, I would love to work with very long focal lengths that allow me to reach objects that I am less used to seeing in photographs But that's just a dream at the moment  |
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I don't really have a favorite focal length either, I have three tubes, one 350 mm, one 580 mm and the last one I'm working with now which is 1000 mm and I think each tube is good depending on the object you're photographing. However, if economy allowed me to, I would love to work with very long focal lengths that allow me to reach objects that I am less used to seeing in photographs But that's just a dream at the moment. |
4.53
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With my IMX492 sensor cameras (ASI 294MM and QHY 294M) I feel comfortable in the range of 650 to 850mm. It is easy to guide and the pixel size matches the focal length very well which is a big plus for NB imaging. Most of the targets I'm interested in fits the frame well in this range. With the equipment I can afford, it is quite hard to get much deeper into space. Expenses start to increase exponentially from there on and I am not sure, that I can hide that much money from my wife  ... Honestly, I never tried.CS Christian |
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It depends of course on which objects to observe or image... Clear sky. Astrarno |
12.64
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| During good and better seeing, nothing beats the C11 @f/10 for my favorite targets, planetary nebulae. |
22.76
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Galaxies are my favorite targets so I like the plate scale provided by an EFL of around 4,000 mm. John |
5.61
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| I like detail in galaxies and planetary nebulae so anything that gives me sampling that will do that under good seeing. Typically that means in excess of 2500 mm. |
8.52
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| I definitely prefer 800-1000mm. I love a high res medium fov. |
16.35
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The question itself prompts lot of other questions, which is great! For me, the underlying question is who are you imaging for? The answer to that one is two-fold a) me b) the general non-AP public (friends/community). Hence I was to go for something dramatic when viewed/printed at 4K resolution. There are two things that I find really dramatic. 1) individual nebulae and galaxies 2) Wide field Milk Way or molecular clouds/IFN For the former, a 4K image with the 6200MM , this means than i can afford to resample x 2. I don't need to go any larger than 30arcmin [if I do - then I can mosaic] and 1arcsec/resolution element is fine. My seeing is generally 4arcsec, and I can get a little back with BXT, leading to a alightly oversampled seeing disk. All leads to a focal length of 1600mm this also matches seeing well. [ But does this mean that I am effectively operating at 800mm? Perhaps the question is more what spatial resolution is your favourite?] For the widefield stuff, I find a 200mm focal length really good. It gives me up to 10deg and with a little more details than the (deservedly popular) 135mm focal length. Most dark nights I run both systems. Part of this might also be ex post rationalisation, as if I loved Newtonians more than thr RC design [I most certainly do not] then I might equally have justified a 800-1200mm focal length range.  CS Brian |
6.06
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I've owned everything from 340mm to 2400mm and all of my best images are in the 1600-2400 mm range. No matter what my seeing is, a smaller image scale gives me more to work with when It comes to squeezing out every bit of detail on the smaller objects. Anything more gives me too small a fov, anything less than 1000 just doesn't impress me. After one or two images I go back to the bigger scopes with longer focal length. To be honest the diameter of the telescope matters more to me. I'd rather not touch anything under 10" anymore. There's way more opportunities to image unique objects with bigger telescopes. That's where I want to be. I love seeing everyone else's widefield pics though . |
6.32
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800 to 1000mm 0.7 to 1.0"/pixel That would be my sweetspot More than that would make me too worried about seeing and guiding (unfortunetly I do not own a SB, AP or 10u mount) Besides what makes me excited is how much detail I can take from my setup and at that range and image scale you can a lot But I do enjoy wide field like 100-200mm |
3.94
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For me it is more about equipment I love to handle.... I do own a very well built 1000mm F4 Newton and I enjoy using it and the high resolution of the images it gerts me because of it's 10" opening. I also have a deep love/hate relationship with my 525mm Hyperstar EdgeHD, build like a tank but needs (lots of) love to get acceptable stars; but it gathers light like crazy. This year I have so far used it with long focallength, but soon I will be back to 525mm, let's see what gets the upper hand, the love or the hate part.... Michael |
0.00
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I love my well built 800-1000mm Newtonians, with a modern CMOS they have the perfect resolution for the seeing conditions in Central Europe and the FOV is so versatile you can photograph any object (apart from M31 and some others of this size) and it's neither to small nor to large in the frame. Jan |
5.80
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Four things determine my preferred focal length. 1. Seeing. My seeing is average to poor. Limited aperture and shorter focal length help combat that. 2. Light Pollution. I have to use na rrowband and LRGB for galaxies render poor results. 3. Subject. Imaging primarily in narrowband, I am interested in wider field view of Nebula and as stated above, galaxies are not a real option. 4. Optical quality. Obtaining excellent optical quality in shorter focal length refractors is doable for me ( AP130GTX at f4.5, FSQ106ED at f3.6, used Srellare Officina RH200 at F3) I have an Edge 8, C9.25 & 1.C11. I do use the C9.25 at F6.3, but only for galaxies at dark skies.. And the optical guality is inferior. To obtain a high quality Dall-Kirkham would run $15 to $25k, not mention the mount and camera for it. If I had been able to retire in New Mexico, US, this criterion would all change. Lynn K. |
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My favorite focal length is the shortest focal length that allows my images to be seeing-limited in all but exceptional conditions, in order to get the best balance between resolution and field of view. For my IMX183-based camera, it is 750mm (0.66"/pix). If I make the move to an IMX571 then it would be 1200mm (not a coincidence that I've a 250/1200 astrograph under construction  )
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2.10
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| The target more often than not dictates the FL required for a suitable image. It's for this reason I shoot two rigs. One at 840mm (SW Esprit 120ED) and the other at 1625mm (RC8). My travel scope is a Z73 at 440mm but I don't travel to image much. As I purchased a new telescope I tried to double my existing FL. Looking forward to galaxy season! |
