EXPLORE SCIENTIFIC 127MM ED FCD100 REFRACTOR

[johnturley]

Just over 12 months ago, I purchased an Explore Scientific 127 mm triplet APO, which I mounted on top of my 14in fork mounted Newtonian Reflector. This provides wider low power fields of view, both visually and photographically, than is possible through the larger reflector, and under less than perfect viewing conditions, can provide better views of planets. I was quite pleased with the performance of this refractor, especially as it showed little false colour, and was in fact better colour corrected than an early version Astro Physics 6in Refractor that I once owned.

Shortly after I purchased this instrument, Explore Scientific brought out an improved version, which utilised the better colour corrected FCD100 glass in the lens, and the 2.5in Hex Focuser. At the time wished I had postponed my initial purchase until then, however last month one of the major telescope retailers had a weekend sale offering 15% off on these models, and possibly against my better judgement decided to splash out and upgrade.

The FCD100 lens definitely appears to be better colour corrected, whereas the previous instrument showed a slight trace of false colour on the lunar limb, the new instrument showed none, but it remains to be seen whether there will be much difference in planetary performance.

I must however confess to being rather disappointed with the 2.5in Hex Focuser, especially bearing in mind the large premium (around £350) ES charge to have this on the standard FCD001 version. I did hope that there would be more distance of travel on the focusing mount, but it remains the same at just 45mm, which I consider to be inadequate. In my opinion the optical tubes on ES APO Refractors are about 50 mm too short (maybe to accommodate bino viewers), requiring the use of extension tubes even if using a star diagonal, and the tube on the FCD 100 version was actually 25 mm shorter still, although this was partly offset by the focusing mount being about 10 mm longer. Furthermore although the hex focuser may, as stated by ES, support a heavier load of photographic equipment, and provide a wider unvignetted field of view, I did not find it to be as smooth as the standard 2in version (maybe due to the greater surface area), and moreover I thought that the knobs had a more plastic feel to them. In fact if it had been a simple job, and could have been done without affecting the collimation, I would have been tempted to swap the lenses over between the OTA's.

I would be very interested to hear what other owners think to this refractor, the hex focusing mount, and how they feel it compares to the standard version with the FCD01 glass.

[25585]

Impressive looking set up! Are you considering upgrading or swapping focusers for your newer ES127?

[johnturley]

On ‎15‎/‎02‎/‎2018 at 20:33, 25585 said:

Impressive looking set up! Are you considering upgrading or swapping focusers for your newer ES127?

Probably not, the reason for the upgrade was both a better quality lens and focusing mount, and although the lens is definitely better colour corrected, I did not think that the focusing mount was much of an improvement, if an improvement at all. You pay about £350 extra for the Essentional FCD001 version with this focuser, and yet you can get a (presumably) much better Moonlight focuser for around the same price to fit Skywatcher Refractors and SCT's, but as far as I am aware there is not one available to fit ES scopes.

[johnturley]

On ‎17‎/‎02‎/‎2018 at 12:08, johnturley said:

Probably not, the reason for the upgrade was both a better quality lens and focusing mount, and although the lens is definitely better colour corrected, I did not think that the focusing mount was much of an improvement, if an improvement at all. You pay about £350 extra for the Essential FCD001 version with this focuser, and yet you can get a (presumably) much better Moonlight focuser for around the same price to fit Skywatcher Refractors and SCT's, but as far as I am aware there is not one available to fit ES scopes.

It's looking like Explore Scientific may have been reading some of my posts, as looking at Telescope House's website today, the price of the Essential FCD001 version with the standard focuser has been increased by about £70 to £1,330, but the version with the 2.5in hex focuser reduced by £200 to £1,420, so they now charge only a £90 premium for the hex focuser.

[Ricochet]

I've got the hexafoc on my dob and I don't think there's really anything wrong with it. As for the roughness that you are reporting I would check that you've undone the locking screw on the underside of the focuser and test again to see if that makes a difference. Also there is a plastic "cap" at the end of the fixed part of the draw tube. Mine was catching on the moving part of the draw tube and so I took it off and filed the corners a bit where it was catching. 

[johnturley]

3 hours ago, Ricochet said:

I've got the hexafoc on my dob and I don't think there's really anything wrong with it. As for the roughness that you are reporting I would check that you've undone the locking screw on the underside of the focuser and test again to see if that makes a difference. Also there is a plastic "cap" at the end of the fixed part of the draw tube. Mine was catching on the moving part of the draw tube and so I took it off and filed the corners a bit where it was catching. 

I wasn't saying that I thought this focuser was particularly poor, just not a smooth as the standard 2in focuser, and not worth the £350 premium that they were charging to have this fitted on their Essential Version Refractors, however they now appear to have resolved this latter issue to a certain extent.