Astro Tutorial #1.15: Barlow Lens and Focal Reducer

[@texdoms]

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

[@catchingphotons]

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

[@sk8erfreak7645]

Best channel for 101 info I have found so far!

[@catchingphotons]

Thanks a lot!

[@JarrodMcKitterick]

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

[@catchingphotons]

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!

[@Spamandrice]

Probably the best explanation by far

[@catchingphotons]

Thanks so much!!

[@mikehuber4150]

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]

Thanks Mike for this encouraging comment! Clear skies!

[@andreigrigoras6592]

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

[@catchingphotons]

You are very welcome!

[@thekirigamist]

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

[@catchingphotons]

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

[@thekirigamist]

@@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 😂

[@tamanebp]

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]

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

[@tamanebp]

@@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.

[@myidahohomestead.7123]

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]

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!

[@triops81]

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]

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

[@kyleb209]

Thank you for making this video. Big help!

[@catchingphotons]

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

[@tadsliwak7233]

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]

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

[@ARMadillo18]

Thanks for this video

[@catchingphotons]

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

[@keivanhamidi]

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]

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]

@@catchingphotons thank you so much !!😁🙌

[@pedrol.3733]

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]

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

[@milos-7712]

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]

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]

@@catchingphotons Great! Thx for the answer 🙂

[@nasanction]

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

[@catchingphotons]

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.

[@aurimixas]

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]

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

[@GameTunesOriginal]

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]

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]

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

[@saketkulkarni1238]

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]

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]

@@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]

@@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]

@@catchingphotons yes sure😁👍👍

[@maximuscassius3121]

Hey Dude, thanks for the math class😒

[@catchingphotons]

😅 you are very welcome!

[@robinj.9329]

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.

[@abrarahmad5121]

Crux of this video is here 11:08

[@catchingphotons]

Because it's a massive oversimplification?

[@143maverick]

learnt a lot , Thanks ❤

[@catchingphotons]

You are very welcome!