Baader VIP 2x vs Baader/Zeiss Barlow

[Piero]

I thought it would be curious to report my thoughts about these two fine barlows: The Baader VIP 2x (here called VIP) and the Baader / Zeiss Barlow 2x (here called BZ). This prefer to write these comments gradually, so I apologise if the information will be a bit  spread throughout this thread. 

Both these barlows are Baader modular systems, meaning that their magnification factor can be changed with spacers.  

The VIP is made of a 2"-to-1.25" adapter, 1 ring converting M-48 filter thread to T2, two 15mm T2 spacers, and finally a T2-to-1.25" nosepiece containing the barlow lens. The barlow is placed on the top of this nosepiece. Removing the two spacers transforms the barlow into a 1.5x amplifier, whereas removing just one spacer will transform it into a 1.76x. Of course additional spacers can be added. 

 

The BZ 2x is made of a Baader click-lock (which has a removable T2 ring on top if needed), and a long T2 nosepiece containing the barlow lens. In contrast to the VIP, here the lens is placed at the bottom. Extra spacers can be added between these two components, increasing the barlow factor.

 

The position of the lens has advantages and disadvantages.

- Advantages (VIP): The nosepiece is filter-threaded. The 2-to-1.25" adapter is handy as it allows one to insert the VIP into the focuser. Factors of 1.5x and 1.76x can be useful in many cases.

- Disadvantages (VIP): the barlow will require a bit of inward refocus. One can run out of (in) focus when many extra spacers are added.

- Advantages (BZ): the barlow is essentially parfocal at 2x and is short even when some spacer is added. Basically one can reach 2.6x, 3x, etc configurations quite easily. 

- Disadvantages (BZ): there is no filter thread at the bottom and cannot accommodate factors smaller than 2x (e.g. 1.5x-1.75x).

Cost is different between the two. As of today, the VIP costs ~£180, whereas the BZ ~£370.

 

First test using my TV60 in day time.

First of all, one of my concern was the length of the BZ. This enters completely into a 1.25" TV everbrite without touching the mirror (note that there is a smaller extension of about .5cm at the bottom of the nosepiece where the lens is. This does not touch the mirror).  

Optically, I tried my very best to spot some difference between the two using my Vixen SLV 9mm. After spending 1.5h, I simply couldn't. There were times when I actually had to look at which barlow was inserted into the diagonal, because the views were nearly identical. Their usability was very different though. The VIP required the coarse focuser to be almost fully retracted inward, so testing my Vixen SLV 5mm (72x) against Vixen SLV 9mm + VIP 2x (80x), was a bit challenging with the TV60. I felt the only way to potentially spot a difference between these two barlows was to really push the magnification. Therefore I took the best eyepiece I have, the Vixen HR 2.4mm (150x). The plan was to test colours and shapes of leaves at 300x (127 inch/aperture). After swapping the two barlows 3-4 times, it appeared to me that the views in the BZ were slightly better than the VIP. The difference was not obvious though. The colour tint was essentially the same to my eye. The shapes of leaves appeared slightly more defined instead. 

First impression. The BZ barlow 2x is more comfortable to use in the field than the VIP because it doesn't move the focus position. The issue with the VIP is that it can move the focus a lot. The flexibility of the VIP comes in with zoom eyepieces like the Leica and the Zeiss because one often wants the flexibility of 1.5x-2x factors via spacers. With a zoom, the change in focus position is less relevant because once the zoom is in the focuser, one just zooms in or out, but doesn't change the eyepiece. 

[John]

Very interesting initial report Piero

I will be waiting to hear what you think when you get them under the stars.

[Piero]

Saturn:

The Vixen 9mm + BZ 2x (80x) showed the Cassini division on the outer part of the rings. One belt was also visible as well as Titan of course. The BZ came to focus very precisely like the Vixen HR 2.4mm: the margin when the image is perfectly focused was very narrow. The VIP was also precise, but I felt the BZ was a tiny bit more. Comparing the two barlow was not easy due to the change in focus position for the VIP. Unfortunately my TV60 didn't come to focus when the VIP is in 2x mode. One way to work around this inconvenient was to configure the VIP at 1.5x and place it before the diagonal. This mode required the extraction of the whole coarse focuser. Doing so, the VIP used the path of the diagonal as spacer. As this distance was certainly longer than 30mm (which makes the VIP a 2x barlow), I used the two 15mm spacers of the VIP as extra spacers for the BZ. Doing so, the BZ became ~2.45x (mag: 98x), whereas the VIP was around ~2.6x (mag:104x). Of course the TV 1.25" Everbrite diagonal was cleaned. The views revealed similar details, albeit the slightly increase in size for the VIP. At this magnification and under this okay-ish seeing the Cassini division was still detectable with a bit of effort. A bit of grey scale tones was also visible on the rings. A hint of the shadow of the planet on the ring was also noticeable. The colour of the equatorial belt was rather distinct. Titan appeared as a pin point star. All these details were also visible using the Vixen 9mm + BZ 2x at 80x. 

Second impression: both these barlows are very fine optically. I really like the BZ.

Here is a picture of the two barlows showing their size: