What is the difference between Barlows, Focal Extenders and Focal Reducers?

[@paulhathaway6292]

Very helpful Bogdan. Well done.

[@krystianciesiun5483]

Hi! please add more vid’s. The most substantive and comprehensive yt channel on astronomy. ;)

[@edf2953]

Hi Bogdan. This is the best comparison video of Barlow lenses, focal extenders and focal reducers that I’ve ever seen on KZbin. You did an excellent job in explaining the differences and benefits and considerations. Great job. I also just watched todays video on getting ready for Saturn’s viewing opportunity later this month. That was another fine production which I found very informative and interesting. Thanks for sharing your knowledge with the community.

[@SpectreLX]

Truth: every additional lens - reduces the image quality! 👍👍👍 Thank you!

[@wessauder7708]

Thank you for such a detailed explanation. What a timely video! I bit the bullet and bought the 2" 2x Explore Scientific Focal Extender recently and it worked extremely well - I was nervous but the quality of the build, flexibility with my eyepieces and great star gazing experience really showed me I bought a great quality piece worth the price (NEAF Sale!). I was curious what the difference between the Barlow and the Extender were and I'm really glad I went with the extender. For reference, I have a vintage C8 Celestar Deluxe which I just purchased as well as several luminos eyepiece (7,10 and 23mm) along with a 2" Celestron Dielectric diagonal. Clear Skies!

[@schotoka]

Thx for the video. I got myself an omegon reducer to experiment with my MAK. Just waiting fo clear skies.

[@SuzanneWhitehead-ot9fi]

Helpful and detailed explanation! Thank you!

[@DoronTshuva770]

great video, when I see more then 2 that are 100% I usually subscribe. thank you for the good work. does more Barlow give more eye relief?

[@BogdanDamian]

@DoronTshuva770 Grad you like the video! More Barlows do not necessarily increase the eye relief. It can happen, but it depends on the optical properties of the lenses.

[@DoronTshuva770]

I see, not all lenses are made equal I suppose. I use to study optics in physics class but now there's so much more I don't know then I know

[@kellytaylor3915]

I like the Vernonscope MDB 1 1/4” they thread into your eyepieces that have standard or Vernonscope ( Brandon ) threads. My scopes are all F/9 or longer ratios. The MDB 1.25x or 1.5X can be combined to make a 3X or a 2.75x or 2.5X The cost is very good and the glass is excellent. After viewing for many many hours at the eyepiece of my scopes. The MDB gives me the ability to see how good the seeing is on any given night. I have other eyepiece brands. When I want to forget about the glass and just view all I can see with the conditions There is a Brandon Eyepiece in my scope. Then maybe a MDB Vernonscope Barlow as well. More talk of exit pupil and F/ratios need to be discussed. Framing your viewing object with the FOV of Eyepiece in use. Eyepieces and good filters give you choices most did not know they had. When one of the world’s best visual observer was asked the question. ( How did you deal with the color on those old refractors at Harvard? ) His response was. #11 yellow filter. Also a #8. I learned a lot about filters. The UV/IR filter should be in every visual observer’s Eyepiece case. I believe in Not letting a camera and computer have all the fun. Get a good comfortable position and study what you look at. Let your eye adjust to what is there! Most of all have fun! Over 40 years of viewing. 1,000’s of hours at the eyepiece. For me it never gets old.

[@curronhill2744]

Thank you, very informative!

[@vitalieBu]

Thank you so much for explanation! I have one 14" Dobsonian F/4.6 with 1650mm FL and one 12" LX200 SCT F/10 with 3048mm FL ... using a 30mm 82° ES eyepiece I can see beautifully the entire double cluster in Perseus only in the 14" dobsonian...but with the same eyepiece on the 12" SCT ... only one cluster at the time .... the same for Andromeda Galaxy...with a shorter focal length I see more of it. I don't do Astrophotography...I'm more of a visual observer... I guess I'm gonna get one of those Celestron Focal Reducer/ Corrector F/6.3.

[@lavers_1]

thanks for this information. Excellent channel!

[@KingLoopie1]

Thanks for the solid info! 👍

[@MountainFisher]

I seldom use Barlows except with my larger Orthoscopic eyepieces, brings in planets very well. I never thought about focal extenders at all not knowing the difference, well now I know and at present do not find myself in need of one, but I'm getting an Apo 102mm F7 and we'll see how that works out with 2" eyepieces. I have noticed simple polarizing filters or a cheap broadband helps kill fringe on planets and the Moon when placed in the Barlow. I use a Shorty from time to time plus the tall TV 2x.

[@editplayerog]

can I Make Spotting Scope Since Spotting scopes are so Expensive if we see celestron gosky Brands i Want To viewing birds , mountains And little bit of Astronomy like moon Saturn and i have A Objective lens of 500mm focal length and 70mm diameter So Can I Use Short Focal Length tube To Use it under 100mm tube with Barlow ?

[@alexsoma3720]

Thank you for yet another great video! I have a request if I may: could you review the Oberon series from Omegon? I cannot find anything on those anywhere... And I would love to see a review from you. Anyway, thanks again for all your great work!

[@jasonspringfield5601]

Thank you for the video. I have a C8 SCT. I'm trying to do planetary imaging using the ES 2X focal extender and a DSLR plugged into it, but I can't get it to focus. I noticed other astrophotographers tend to use Barlows combined with an astrocamera screwed on for planetary imaging, and I'm thinking that I should buy a barlow with threads. Can you, or some of the experts in the comment area, explain if Barlows should be used for astrophotography instead of focal extenders and why? Thanks for the help.

[@BogdanDamian]

@jasonspringfield5601 Hi Jason, I don't think that using a Barlow instead of a focal extender would necessarily solve your focusing issue. It sounds like you just need to increase the distance between the camera's sensor and the telescope. I had the same issue with my refractor and I ended up adding several centimeters worth of extensions just to get the image into focus. Try moving the camera away from the telescope by hand millimeter by millimeter while keeping it aimed at the target and see how far away you need to pull it back until the image gets sharp. You can do this during the day while aiming at a far away target (> 2km).

[@mihaitaene4644]

Buna dimineata, Dl. Damian . Sunt incepator si am un refractor Bresser Taurus 90/900 mm. Cum as putea sa l imbunatatesc pentru observarea DSO ? Am 2 oculare Kellner de 20 si 4 mm. Ma puteti ajuta ? Multumesc frumos . O zi buna !!

[@BogdanDamian]

@mihaitaene4644 Buna seara. Diametrul de 90 mm al telescopului dvs cam limiteaza DSO-urile care pot fi observate. Cele mai luminoase dintre ele precum M42 sau M45, insa ar trebuie sa mearge fara probleme. Pentru a inbunatatii imagina as recomanda schimbarii diagonalei ce a venit cu telescopul cu una mai de calitate. De preferinta una cu o prisma inloc de oglinda. Si inlocuirea ocularelor cu altele mai de calitate poate duce la o imagine mai deschisa si cu mai mult contrast. Aicea depinde de ce piese aveti deja si cat de mult sunteti pregatit sa investiti in accesorii noi. Insa cel mai mare effect pozitiv asupra imaginii este locatia telescopului. Un mediu rural va oferi intotdeauna un cer mai clar si intunecat decat la oras.

[@mihaitaene4644]

@@BogdanDamian . Multumesc frumos !!

[@mihaitaene4644]

@@BogdanDamian . Buna dimineata , Dl. Damian. Am gasit de lucru ,ca sudor electric, in Olanda si de Craciun as vrea sa cumpar un telescop mai performant. Ce puteti sa mi recomandati ? M ar interesa ceva bun si vizual si astro foto . M as incadra undeva pe la 600 € . Multumesc frumos. Sanatate multa !!

[@ivanluhi]

Nice! Exactly the explanation I was looking for! Is a focal extender preferable to a Barlow for astrophotography/EEA?

[@BogdanDamian]

@ivanluhi Glad you found the video useful. For astrophotography I would recommend a focal extender because it won't extend the focal plane as much as a Barlow, making it easier to achieve focus with the camera attached.

[@ivanluhi]

@@BogdanDamian thank you for the tip, I didn't knew that!

[@elray4932]

Very thorough, excellent review. Would a focal extender be brighter than a Barlow or a PowerMate?

[@BogdanDamian]

@elray4932 A premium Barlow might be a bit brighter than a medium tier focal extender, but comparing same tier items, the differences will probably be negligible. A powermate is just the focal extender from Tele Vue.

[@elray4932]

@@BogdanDamian Thank you!

[@anthony2786]

I have a Discovory Sky T50 and it comes with a H20mm and F6mm eyepieces. Can i buy and use other eyepieces or it depends on the diagonal mirror?

[@BogdanDamian]

@anthony2786 Hi, yes you can use other eyepieces. Your telescope features a 1.25" diagonal which means that you can use any 1.25" sized eyepieces.

[@anthony2786]

@@BogdanDamian Thank you so much

[@sudarshan273]

A totally beginner question - can I build a complete eyepiece set with a single eyepiece (of say around 3mm exit pupil) and multiple barlows 1.5x, 2x, 3x and focal reducers etc?

[@sudarshan273]

The reason I ask this is because I was wondering if premium eyepieces are very expensive, why not get just one premium eyepiece and get multiple barlows and focal reducers which are relatively cheap. Instead of changing eyepieces everytime you want to change the magnification, you could change the Barlow instead. Lol

[@BogdanDamian]

@sudarshan273 In theory it should be doable. At least partially, but it is probably going to be very impractical. You will need to give up some flexibility and get premium focal modifiers. The compatibility with diagonals will also suffer since the focal modifiers probably won't fully fit inside. You would be also limited by the field stop if you choose a 1.25" eyepiece. If you go for a 2" eyepiece that features a very wide field stop, then you'll have to work only with focal reducers, which could be difficult to pull off. Interesting question though 🤔

[@sudarshan273]

​@@BogdanDamianThank you for your insights. To overcome some of the issues you mentioned, please consider the following combination instead. I have an 8f6 dob and 2 mediocre plossls that came with it. To upgrade it- A TV 24 Panoptic + 2x, 2.5x, 3x and 4x focal extenders. TV 24 Pan gives 1.36° TFOV and 50x mag. That's pretty much the widest and lowest I need to go. TV 24 Pan + 4x FE gives same magnification and similar TFOV as that of TV 6 delos. Similarly, TV 24 Pan + 3x FE = TV 8 delos, TV 24 Pan + 2.5x FE = TV 10 delos, TV 24 Pan + 2x FE = TV 12 delos. I checked the math of magnification and TFOV on a simulator. I understand that the performance would not be to the level of separate eyepieces. But it should be pretty close with decent quality FEs like Explore scientific. Any thoughts? Am I crazy here?

[@sudarshan273]

​@@BogdanDamian This solves the 1.25" vs 2" conundrum. Also there is no need of premium focal reducers.

[@efx245precor3]

And 4 element Powermates

[@kevkef300]

I have a question about the Focal Extenders. Is it possible to use it in combination with a barlow lens? For example, I would use the 2x barlow lens with a T2 Ring adapter for my DSLR camera. I already try it with a 2x barlow lens, T2 ring adapter and a DSLR camera to capture the moon. I have a 750mm telescope. But I just recently found out that I couldn't find Saturn (August 27th) even with a barlow. Hopefully the community can help me out. And if it's possible/compatible, that would be easier to make the choice.