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Astro Tutorial #1.15: Barlow Lens and Focal Reducer

Hey folks,
in this video we will cover two additional lenses we mentioned here and there in previous videos: Barlow lenses and (focal) reducer.
We will go though
- the light paths and behind the scene theory
- effects on our optical setup including the use with eyepieces and cameras
- changes and calculations in / for "magnification" and the "FOV"
- practical applications for beginners
- optical limits
- ... much more.
I hope you find this video useful. And as always I say: Clear skies everyone and till next time here on catchingphotons!
-Chris
Links:
Optical simulator I used within this video:
- ricktu288.gith...
Trevor talking about the Celestron HD11
- • Building a Telescope R...
Copyright:
creativecommon...
creativecommon...
creativecommon...
creativecommon...
Hashtags:
#barlow
#reducer
#telescope
#barlow_lens
#focal_reducer
#barlowlens
#focalreducer
#FOV

Пікірлер: 60

  • @Spamandrice
    @Spamandrice5 ай бұрын

    Probably the best explanation by far

  • @catchingphotons

    @catchingphotons

    5 ай бұрын

    Thanks so much!!

  • @texdoms
    @texdoms3 жыл бұрын

    Thanks for the information on Barlow lens, I learned a great deal.

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Thanks for the comment! Glad the video was of any help! Clear skies!

  • @sk8erfreak7645
    @sk8erfreak76453 жыл бұрын

    Best channel for 101 info I have found so far!

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Thanks a lot!

  • @andreigrigoras6592
    @andreigrigoras6592 Жыл бұрын

    Finally! I understand the telescope I have. Thank you very much

  • @catchingphotons

    @catchingphotons

    Жыл бұрын

    You are very welcome!

  • @JarrodMcKitterick
    @JarrodMcKitterick3 жыл бұрын

    Thank you! Excellent series of videos. Also, the background music reminds me of EVE Online. Good stuff!

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Thanks njoobie for the comment, glad I could help :-) I (sadly) don't play EVE, so I can't know. I wanted something relaxing and not distracting to fill the background. Glad you like it. Clear skies!

  • @mikehuber4150
    @mikehuber41503 жыл бұрын

    Instasub. This single video answered all the issues I've been having since starting astrophotography that no other source has been able to answer. Off to buy my first barlow and focal reducer. Thank you!

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Thanks Mike for this encouraging comment! Clear skies!

  • @thekirigamist
    @thekirigamist3 жыл бұрын

    I have actually sawed one. Felt it when you mentioned.

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Oh really? I think I would be way too scared to screw anything up!

  • @thekirigamist

    @thekirigamist

    3 жыл бұрын

    @@catchingphotons I built one. 8" dob. It's held together in very scary ways already. But works like charm. Once I was at a point where I had to get closer to the focus. So I went for it. My hands don't tremble for any brutality since that assault 😂

  • @ARMadillo18
    @ARMadillo182 жыл бұрын

    Thanks for this video

  • @catchingphotons

    @catchingphotons

    2 жыл бұрын

    You are very welcome! Thanks for your kind words, very much appreciated.

  • @tamanebp
    @tamanebp3 жыл бұрын

    I knew of barlow but had never heard of reducers, great info! I have an 8 inch dobsonian, so I may look into a reducer.

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Thanks for your comment! What's the focal length of your scope? Clear skies!!

  • @tamanebp

    @tamanebp

    3 жыл бұрын

    @@catchingphotons She's got a whopping 1200mm FL. I've got 2 eyepieces currently: a 25mm and a 10mm. I find myself rarely using the 10. In fact, I want to get a wider view eyepiece soon since I enjoy open clusters a lot.

  • @kyleb209
    @kyleb2093 жыл бұрын

    Thank you for making this video. Big help!

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    You are very welcome! Glad the video was of any help! Clear skies to you!

  • @myidahohomestead.7123
    @myidahohomestead.71233 жыл бұрын

    I have a 12 inch newtonian. There isn't a camera ive tried that will come into focus without a Barlow. Its very disappointing because it gives me way too zoomed in images. I can't fit the moon in one shot. And it makes getting perfect focus harder having everything magnified that much more

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Yes I understand that. On the other hand: imagine your focal length doubled or tripled by a high quality barlow! Planets will be super detailed (given ok'ish seeing)!! One of my next scopes will be a SCT or a MAK for planetary imaging. I like my 750mm newtonian scope but having... like 2000mm native focal length would be super epic! Clear skies Daniel!

  • @spacemanschannel6380
    @spacemanschannel63803 жыл бұрын

    Hi Chris, do I understand correctly: use Barlow lens for small objects like planets, and reducer for big objects like nebula (Messier objects)? I have a Skywatcher 150/750 like yours. 😊

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Jea that's basically it :-) Tip of the day: Download >Stellarium 1) and reducer (

  • @triops81
    @triops812 жыл бұрын

    Great video. Would you please make a video about other types of focal length multiplier, and there differences? I am confused about the available options like Barlow, powermate, telecentric focal extender.

  • @catchingphotons

    @catchingphotons

    2 жыл бұрын

    Thanks for the advice - will consider it in the future! Clear skies!!

  • @pedrol.3733
    @pedrol.3733 Жыл бұрын

    Hello, I have a question, I have a 300m 76m telescope, I bought a 3x barlow which I don't focus in any way, looking on youtube I found a person who said that the barlow was very small and I had to lengthen it to 11.5cm high, which I did and it worked perfectly for me with the 20mm eyepiece and with the 4mm eyepiece, when you set it to the maximum, you can see that it lacks a bit for it to focus, which makes me wonder if the barlow lengthens more, but I don't know if it will lose much of its range, both eyepieces work well If I remove the barlow lens and put it in the screwed eyepieces but the range decreases.

  • @catchingphotons

    @catchingphotons

    Жыл бұрын

    It has something to do with the focus point of the barlow. Can you provide a link to it? Cheers!

  • @tadsliwak7233
    @tadsliwak72333 жыл бұрын

    You mentioned trying to make a fast scope, f/2 would be bad idea based on the quality of the lens; but how about taking a f/15 to f/7.5 with a 0.5 reducer? I got a Meade ETX125 from work, just trying to see if i can make it faster; or save the money for an actual faster scope? Beginner here.

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Just give it a go - maybe it works. It's just that f/7 scopes are made for f/7 and this scope is f/15 (witch is great for its own purposes). This scope should be great for any planetary - and there you could add an additional 2x barlow (and not a reducer) to get extra close! But anyway: If the reducer is of great quality, if (!) the coma at the edges don't dominate the extra gained field of view - maybe it's worth a shot. Clear skies! -Chris

  • @143maverick
    @143maverick Жыл бұрын

    learnt a lot , Thanks ❤

  • @catchingphotons

    @catchingphotons

    Жыл бұрын

    You are very welcome!

  • @milos-7712
    @milos-77122 жыл бұрын

    Fantastic video series! I've been watching all of them and I've learned more from them in a day, than watching other videos without form like this. One question though. Is there a way to know how much exactly can you take down your F? For example If I stick a 0.5x reducer on 3 skywatcher newtonian telescopes 200/1200 (F6 to F3) 200/1000(F5 to F2.5) 200/800(F4 toF2) How do you know when the reducer starts to have a bad impact on the image? Or is the low F itself the issue, no matter the scope? Thanks in advance 🙂✌

  • @catchingphotons

    @catchingphotons

    2 жыл бұрын

    Hey Miloš, no the low f-ratio itself is no problem. Lenses of good quality go down to f1.2 or crazy stuff like that. The optical quality of your setup MUST be able to handle that though. I don't think you should go below x0.5 with any scope unless the reducer is combined with coma corrector etc to restore optical aberrations. As long as I understand that topic, going too low will ultimately mean shrinking the light cone within your scope: skyandtelescope.org/astronomy-blogs/imaging-foundations-richard-wright/how-focal-ratio-affects-your-astro-images/ Clear skies!

  • @milos-7712

    @milos-7712

    2 жыл бұрын

    @@catchingphotons Great! Thx for the answer 🙂

  • @keivanhamidi
    @keivanhamidi3 жыл бұрын

    I have also a 150/750 and I am planning to buy a .5x reducer for a while field for astrophotography (especially to shoot very big objects like m42, m45, m31...). So it should work okay, right?

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Hey Keivan, a x0.5 reducer will drop your f-ratio to f2.5!! That is pretty fast and you need to take every misalignment and imperfection into account. Means: A very (!) good and perfectly aligned coma corrector and so on. Make sure everything is well in place :-) Clear skies!

  • @keivanhamidi

    @keivanhamidi

    3 жыл бұрын

    @@catchingphotons thank you so much !!😁🙌

  • @aurimixas
    @aurimixas3 жыл бұрын

    My reflector telescope is f/9.3 and focal lenght 1400mm. My lowest power eyepieces are 20mm and 25mm. Will getting 0.5x reducer from amazon for 30$ work instead of getting 40mm and 50mm eyepieces for galaxies and nebulas?

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Hey auri, 1) f10 won't give you a pleasant view of faint DSO's. For visual, f10 and 1400mm is a planet scope. I own a 150mm aperture 750mm focal length f5 reflector and orion nebula and andromeda is the deepest I get. It depends on your location though - maybe you have more luck in the central Australian desert ;-) 2) Any proper eyepiece will be superior to the combination eyepiece - barlow. This is simply due to the lower number of optical components. But having 3 eyepieces and adding one single barlow will increase your focal lengths to 6 (for the price of one). So that might be within consideration. 3) 30$ barlows are normally (!) within the lower price segment. Test it, but don't expect the world. Clear skies man! -Chris

  • @robinj.9329
    @robinj.9329 Жыл бұрын

    I have never, in nearly half a century of telescope use, used a barlow! This is likely due to the fact that, in the 1960's when I got started, most "Barlow" lenses were NOT of very good quality. And thus were to be avoided by the "Serious" Astronomer.

  • @nasanction
    @nasanction2 жыл бұрын

    What if you turned the Barlow lens the opposite direction? Would it become a reducer?

  • @catchingphotons

    @catchingphotons

    2 жыл бұрын

    Nope. Turn a perfect lens around and it will still be the same lens... But modern lenses are glued in a specific order so turning them around might just result in nothing but nonsense 😅 just keep them the intended orientation.

  • @saketkulkarni1238
    @saketkulkarni12382 жыл бұрын

    in 4:07 if we add barlow lens, so it would increase the focal length of the instrument which in turn would increase the magnification...so wouldnt image be blurred ?.....i think we should increase magnification if its necessary....am i right ?

  • @catchingphotons

    @catchingphotons

    2 жыл бұрын

    An additional Barlow lens will increase the magnification by increasing the focal length. That might be intended because you want to observe smaller things. But if you use a Newton telescope not suited for astro-imaging and you can't reach focus than you can use a 1.5 Barlow to "stretch" the focal point out of the focus tube and hence enables you to use the scope at all. Clear skies!

  • @saketkulkarni1238

    @saketkulkarni1238

    2 жыл бұрын

    @@catchingphotons oh i see, now i understand...thanks 😃and one more thing i just finished your playlist..and it was great...believe me or not...whenever i close my eyes all i could is a dark sky with a lot of stars rotating around the zenith (i hope you understand what i am telling😅 ).....it's just beautiful

  • @catchingphotons

    @catchingphotons

    2 жыл бұрын

    @@saketkulkarni1238 Haha, thanks a lot! I wish you many breathtaking hours under dark skies! And whenever you take images: Tag me here or on Twitter! I like to see them!

  • @saketkulkarni1238

    @saketkulkarni1238

    2 жыл бұрын

    @@catchingphotons yes sure😁👍👍

  • @GameTunesOriginal
    @GameTunesOriginal3 жыл бұрын

    If im using a Scope with high focal length for example for planetary observation, something like a 1500 mm Maksutov, is it useful to buy a focal reducer to try to watch galaxies and other dark deep space stuff or am I just wasting money and would be better of saving for a second telescope?

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Watching galaxies requires a big aperture and a short/intermediate focal length. Most people go with "Dobsons" for visual DSO observations. Those Newtonian reflectors have huge apertures and are fitted into rather simple and inexpensive mountings. "As the old saying goes: If your fist scope is your last scope, something went wrong in the first place. There is always the need for a second scope." :-) Clear skies mate!

  • @GameTunesOriginal

    @GameTunesOriginal

    3 жыл бұрын

    @@catchingphotons ^^ Thanks, seems this could get an expensive hobby. Clear skies

  • @maximuscassius3121
    @maximuscassius3121 Жыл бұрын

    Hey Dude, thanks for the math class😒

  • @catchingphotons

    @catchingphotons

    Жыл бұрын

    😅 you are very welcome!

  • @spacemanschannel6380
    @spacemanschannel63803 жыл бұрын

    Hi Chris. What kind of reducer do you use with your 150PDS? I bought a 0.5x reducer for my 150PDS and was unable to see anything. Maybe I did something wrong. Somebody told me the focal point goes inward and therefore reducers don't work with newtonians.

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    I don't own a reducer for my 150PSD jet. My coma corrector has a factor of 1 (so it lets the focal length untouched). Many correctors have a factor of x0.75 - but they need to be placed precisely in the right distance to the focal point in order to get the required corrections for the coma aberrations. You therefor may need spacer. Keep that in mind. Use a reducer without any additional corrector will make aberrations like coma much more worse than before. Is your scope f5? Than a reducer incl coma-corrector is needed. Do you have any specs? Clear skies!

  • @spacemanschannel6380

    @spacemanschannel6380

    3 жыл бұрын

    @@catchingphotons I have this: www.omegon.eu/flatteners-correctors-reducers/omegon-0-5x-reducer-for-photography-and-observing/p,33219 The description says about 5 cm of backfocus are required. The focusser of the 150PDS is 5 cm long so I still have hope. I think coma corrector is not much an issue because I have a astrocam with a small chip, not a DSLR with a big chip. The aberrations on the edge do not fall into the small chip's FOV.

  • @abrarahmad5121
    @abrarahmad51213 жыл бұрын

    Crux of this video is here 11:08

  • @catchingphotons

    @catchingphotons

    3 жыл бұрын

    Because it's a massive oversimplification?

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