Barlow lens

[Paulgra]

Hi 

I am new to all this and have just bought a skywatcher 6" 750mm f/l. I have a 10mm 25mm and a 6.5mm plossl lenses. I am wanting a Barlow lens and I have seen a Revalation astro 2.5x Barlow lens and a  SVBONY 1.25 inches 3X Barlow Lens which would you recommend

thanks for any advice

 

 

[Ricochet]

Of the two a 2.5x is more likely to be useful, but personally I would be more inclined to buy a 2X barlow than anything more powerful. However, I don't think a barlow has much value with your current eyepieces. If you barlow the Plossl you will probably end up with too high a magnification, and the kit eyepieces aren't that great, particularly the 10mm. I would upgrade at least the 10mm before adding a barlow. An 8 and/or 12mm BST Starguider is a good quality and ergonomically nice eyepiece to use and often chosen as a first upgrade.

[Louis D]

Most 2.5x Barlows measure closer to 2.1x to 2.2x from what I've read.  Regardless, the 6.5mm should provide decent high power views.

I would probably recommend getting a 5mm BST Starguider instead for even higher power (150x) along with a 12mm BST Starguider for a decent mid range eyepiece (63x) to replace the so-so 10mm kit eyepiece.

To get to a very wide field of view, you could get a 35mm Aero ED 2" eyepiece sometime in the future.  Yes, the exit pupil will be 7mm, and it will struggle at bit a f/5, but the wide true field of view for locating and centering objects makes it totally worthwhile.

I've got multiple Barlows and rarely use them.  They're clumsy to add and remove.  When I do use one, I tend to put it in the focuser and leave it, doubling the power of every eyepiece, for a given observing session.

[ballisticbrian]

I have  a question about the 3 x Barlow I have with my vintage 0.96 setup. When adding the Barlow in positioned at the moon, I am having trouble focusing. My instinct is that I have to reel the focus into th scope to compensate for the lengnth of th Barlow. Is this correct? Is the eye piece always fully inserted into the Barlow lens? Beginners guide required! lol

 

[barbulo]

Hi @Paulgra and welcome to SLG. 

A piece of advise from another newbie based on own errors: don't fall in love with magnification. There are plenty of "big" objects that you would miss using a Barlow. I would go for a quality eyepiece as mentioned. 

[Tiny Clanger]

18 hours ago, Paulgra said:

Hi 

I am new to all this and have just bought a skywatcher 6" 750mm f/l. I have a 10mm 25mm and a 6.5mm plossl lenses. I am wanting a Barlow lens and I have seen a Revalation astro 2.5x Barlow lens and a  SVBONY 1.25 inches 3X Barlow Lens which would you recommend

thanks for any advice

 

 

I have a 150mm skywatcher heritage dob , and early on followed the usual  advice to buy a 2x barlow  . I've never liked using it. Even in combination with the 8mm or 12mm BST starguider eyepieces I now own it gives very poor views. Extra magnification is not necessarily the key to better viewing, I'd suggest a better , modest magnification eyepiece would be a more effective investment. The 8mm BST works well in my dob.

By the way, your 'scope is not f/1 , 750mm focal length divided by a 150mm diameter mirror = f5

[RT65CB-SWL]

1 hour ago, ballisticbrian said:

I have  a question about the 3 x Barlow I have with my vintage 0.96 setup. When adding the Barlow in positioned at the moon, I am having trouble focusing. My instinct is that I have to reel the focus into th scope to compensate for the lengnth of th Barlow. Is this correct? Is the eye piece always fully inserted into the Barlow lens? Beginners guide required! lol

 

I hardly ever used a 3x Barlow, or for that matter the supplied 2x one that came supplied with my Prinz Astral 550.

29 minutes ago, barbulo said:

Hi @Paulgra and welcome to SLG. 

A piece of advise from another newbie based on own errors: don't fall in love with magnification. There are plenty of "big" objects that you would miss using a Barlow. I would go for a quality eyepiece as mentioned. 

+1

[Paulgra]

Thanks for advice I bought the telescope second hand and it came with these eyepieces below. Also I have looked at the moon and mars but mars was a waste of time not enough magnification . What would you advice to look at Jupiter and Saturn not in view yet also the magnification of my scope is 300x max with the 10mm I am only getting 75x I presume this is why I thought a Barlow lens would be a good Idea.

[AstroNebulee]

Plus 1 for a x2 Barlow, I use much more than my x3 Barlow which hardly gets any use. 

[KP82]

8 minutes ago, Paulgra said:

Thanks for advice I bought the telescope second hand and it came with these eyepieces below. Also I have looked at the moon and mars but mars was a waste of time not enough magnification . What would you advice to look at Jupiter and Saturn not in view yet also the magnification of my scope is 300x max with the 10mm I am only getting 75x I presume this is why I thought a Barlow lens would be a good Idea.

Among those eyepieces that came with your scope, keep the 25mm and ditch the rest. Like others have said the stock 10mm isn't of high quality. The MA 20mm has bad distortion around the edge of the view due to its optical design. The 10mm erecting is for terrestrial use with a refractor. The 6.5mm plossl has an extremely short eye relief, not comfortable for extended period of use.

Go for BST starguider 8mm and 12mm as suggested by the others. The theoretical max mag of your scope is 300x, but the usual seeing in the UK will hardly allow anything more than 200x most of the time. To view Mars you need to wait for its opposition (next one in autumn 2022) and use somewhere between 200x and 250x. As for Jupiter and Saturn, I personally go between 160x - 190x.

[RT65CB-SWL]

Forget about the 300x max... realistically 200x if you are lucky.

Next, think about upgrading the e/p's. the supplied 25mm is quite good apparently, but unsure about the others.
An improvement would be these... https://www.firstlightoptics.com/bst-starguider-eyepieces.html

 

Your present 'scope should or will show...

• the the phases of Venus.
• Galilean moons & equatorial belts of Jupiter.
• the rings and possibly banding of Saturn and its largest moon, Titan.
• Mars being as small as it is even at opposition, your eyes will need to
  be dark-adapted to reveal some detail.

 

Edited March 20, 2021 by Philip R

[Tiny Clanger]

10 minutes ago, KP82 said:

Among those eyepieces that came with your scope, keep the 25mm and ditch the rest. Like others have said the stock 10mm isn't of high quality. The MA 20mm has bad distortion around the edge of the view due to its optical design. The 10mm erecting is for terrestrial use with a refractor. The 6.5mm plossl has an extremely short eye relief, not comfortable for extended period of use.

Go for BST starguider 8mm and 12mm as suggested by the others. The theoretical max mag of your scope is 300x, but the usual seeing in the UK will hardly allow anything more than 200x most of the time. To view Mars you need to wait for its opposition (next one in autumn 2022) and use somewhere between 200x and 250x. As for Jupiter and Saturn, I personally go between 160x - 190x.

I agree 100% with that. The 25mm 'super' eyepiece is fine, it comes as standard with most skywatcher 'scopes (as does the horrid 10mm one ) but the rest are probably little use.

To calculate the magnification, divide the focal length (in your case 750mm) by the length given on the eyepiece , so 750 / 25= 30x. My heritage dob has the same focal length & mirror size, in the late summer/autumn when Mars was close to us and appeared larger than it does at the moment I was able to see various features on it's surface as dark markings with 8mm, 12mm and 17mm eyepieces, which I could use depended on the stability of the atmosphere rather than anything else. Using a different telescope with a longer focal length, I've managed up to 187x, , but not very often.

There's a thread somewhere on here called something like ' what you can expect to see' , search it out if you've not already seen it. BST starguiders are in stock and available from Alan at 'the sky's the limit' https://skys-the-limit-108154.square.site/shop/1-25-bst-starguider-ed/8

[Paulgra]

Thanks again I will look into getting a bst starguider eyepiece should I go for say a 5mm one or the 8mm/ 12mm as suggested would it be also worth getting a Barlow

Thanks

[Tiny Clanger]

3 minutes ago, Paulgra said:

Thanks again I will look into getting a bst starguider eyepiece should I go for say a 5mm one or the 8mm/ 12mm as suggested would it be also worth getting a Barlow

Thanks

Have you used the 'scope yet ? Did the 6.3mm plossl give you decent views without the telescope tube, mount or tripod vibrating , or the magnification making anything you were hoping to view either too dim , or having it scud across your view so fast by the time you saw it , it was gone ? If the 6.3mm was unsatisfactory , anything even shorter would be more unsatisfactory for the same reasons.

If you've not used the existing eyepieces on a few night time targets , don't buy anything else until you have, it will avoid you wasting your money.

[Louis D]

1 hour ago, Paulgra said:

Thanks again I will look into getting a bst starguider eyepiece should I go for say a 5mm one or the 8mm/ 12mm as suggested would it be also worth getting a Barlow

Thanks

The 12mm will yield 63x, the 8mm 94x, and the 5mm 150x.  Ideally, I'd like to see 75x and 125x which would be 10mm and 6mm for day to day usage.  Splitting the difference, the 8mm at 94x seems like a good bet for a first eyepiece.  If you find yourself wanting a bit lower power most of the time, get the 12mm.  If you think a bit more power is needed, the 5mm would be logical.  Personally, I'd lean toward the 8mm and 12mm combo under UK skies despite my initial 5mm/12mm recommendation.

FLO has a 10% discount if you buy two at once, and they sponsor this site.

[wulfrun]

4 hours ago, Tiny Clanger said:

By the way, your 'scope is not f/1 , 750mm focal length divided by a 150mm diameter mirror = f5

You may have mis-read the OP, I think it's typed as 750mm f/l (F/L) = focal length. Not f/1.0.

[wulfrun]

No-one's mentioned a zoom yet. The Hyperflex zoom would go nicely with that scope, with x35-x104 magnification. OP should be made aware that zooms have a narrower FOV at the longer end though, which is a compromise typical of most/all zooms.

I have the similar 150PL (1200mm F/L) and find one useful. Saying that, last time out I only used a 20mm, 16mm and x2 focal extender and was very happy with their performance. Fixed BSTs or a zoom, either route would be an improvement.

[Paulgra]

25 minutes ago, wulfrun said:

You may have mis-read the OP, I think it's typed as 750mm f/l (F/L) = focal length. Not f/1.0.

Yes that is what I meant 🤣🤣

[Paulgra]

1 hour ago, Louis D said:

The 12mm will yield 63x, the 8mm 94x, and the 5mm 150x.  Ideally, I'd like to see 75x and 125x which would be 10mm and 6mm for day to day usage.  Splitting the difference, the 8mm at 94x seems like a good bet for a first eyepiece.  If you find yourself wanting a bit lower power most of the time, get the 12mm.  If you think a bit more power is needed, the 5mm would be logical.  Personally, I'd lean toward the 8mm and 12mm combo under UK skies despite my initial 5mm/12mm recommendation.

FLO has a 10% discount if you buy two at once, and they sponsor this site.

Thanks for your time and replying to my questions your help is appreciated 🙂

[Spile]

First of all, ignore the rest of this post if you already know it.

Otherwise...

In terms of targets, there are plenty to look at and a search of these forums will come up with lots of recommendations.  I would definitely get a copy of Turn Left at Orion and I would also check out some targets like the Double Cluster, the Beehive and a few coloured binaries like Almach. 

Just be careful of the astrophotographers who lurk in these parts and may try and tempt you to the dark side.

[Neil H]

36 minutes ago, Spile said:

First of all, ignore the rest of this post if you already know it.

Otherwise...

In terms of targets, there are plenty to look at and a search of these forums will come up with lots of recommendations.  I would definitely get a copy of Turn Left at Orion and I would also check out some targets like the Double Cluster, the Beehive and a few coloured binaries like Almach. 

Just be careful of the astrophotographers who lurk in these parts and may try and tempt you to the dark side.

Turn left at Orion is a must , Spile you forgot about the light side ( solar) 

When I had my 150/750 I didn't use a Barlow that much I think seeing was never that good , I don't use it that much now , I do use my zoom a lot even tho it's the cheaper celestron 8 to 24 

Edited March 21, 2021 by Neil H

[Louis D]

I use my 2" GSO ED 2x Barlow with the TV Panoptic Barlow Interface more than any of my 1.25" Barlows because I enjoy being able to use my large array of 2"-only eyepieces at double the power.  As I said above, I just stick the combo in the focuser and leave it for an entire viewing session just to change things up.