Adriano Lolli YTube video on converting the B400 into a B590. Turns out the band filter is large enough to allow for this modification. He also notes about replacing the BG with a higher quality unit. 4 month old video. But the BG replaced might be the older Lunt version. Check out his YTube Channel for details.
Not a diy. Unless you have the tools, skill. Any error by fraction of mm turns your block filter into a paper weight.
Lunt BF400 modification.
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Re: Lunt BF400 modification.
Have you got a link you can share please?
http://brierleyhillsolar.blogspot.co.uk/
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Re: Lunt BF400 modification.
https://youtu.be/G0mp0-BLahU
In Italian. Auto translate can be applied in YT Settings to change the language of the subtitles.
Having watched the video I would suggest extreme caution against simply running a larger drill through the existing hole. Even in a lathe!
Any larger drill, run through the existing hole, will almost certainly produce an oversized aperture.
Similarly, the countersink must not breach the enlarged hole. Merely taper the hole to form the baffle.
A drilled hole will reflect light from the newly cut, parallel surface.
Hence the use of knife-edge baffles as well as matt black paint.
An alternative [skilled] method would be to use a suitable and sharp centre drill in the lathe. While measuring each new cut with calipers.
A centre drill is tapered and very much stiffer than a common twist drill. Cutting oversized is still a VERY REAL DANGER.
Those with the tools and skill could repair an oversized drilled hole with a thin plate having the required finished aperture.
Do not say you have NOT been warned against the dangers of producing a paperweight.
In Italian. Auto translate can be applied in YT Settings to change the language of the subtitles.
Having watched the video I would suggest extreme caution against simply running a larger drill through the existing hole. Even in a lathe!
Any larger drill, run through the existing hole, will almost certainly produce an oversized aperture.
Similarly, the countersink must not breach the enlarged hole. Merely taper the hole to form the baffle.
A drilled hole will reflect light from the newly cut, parallel surface.
Hence the use of knife-edge baffles as well as matt black paint.
An alternative [skilled] method would be to use a suitable and sharp centre drill in the lathe. While measuring each new cut with calipers.
A centre drill is tapered and very much stiffer than a common twist drill. Cutting oversized is still a VERY REAL DANGER.
Those with the tools and skill could repair an oversized drilled hole with a thin plate having the required finished aperture.
Do not say you have NOT been warned against the dangers of producing a paperweight.
http://fullerscopes.blogspot.dk/
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
H-alpha: Baader 160mm D-ERF, iStar 150/10 H-alpha objective, 2" Baader 35nm H-a, 2" Beloptik KG3,
Lunt 60MT etalon, Lunt B1200S2 BF, Assorted T-S GPCs or 2x "Shorty" Barlow, ZWO ASI174.
Re: Lunt BF400 modification.
It's a modification that I have made about 10 years ago and which I have illustrated in an Italian forum in 2016 (modification then made by various other people in Italy)...
https://www.binomania.it/phpBB3/viewtopic.php?t=8371
The advantage of the modification can be seen, compared to the small 4 mm hole.
What is interesting however is that the same thing can be done for the BF1800 with the same methodology, in fact the useful diameter of the BF1800 filter is 19.5 mm, so this BF can be transformed into a BF1900 (perhaps even into a BF1950 ...).
In this case, however, I must point out a ridiculous choice by Lunt in the BF1800 model which does not even lead to exploiting the entire diameter of the BF1800, in fact the IR Cut filter placed at the entrance of the diagonal mirror is approximately 16 mm in diameter, therefore smaller than the 18 mm of the BF and this brings vignetting.
I'm making a tilt adjustment ring to use the BF 1800 filter off its diagonal mirror, so that I can rotate it and use it across its entire diameter (building a new tilting like this viewtopic.php?p=156165#p156165).
Those who do not want to do this, but want to make the most of their B1800 should first eliminate the restriction, widening the entrance hole of the diagonal mirror and inserting a new IR Cut filter at the input by installing a 1.25" IR Cut filter, type UV-IR CUT with KG3 by Smie, or similar.
https://www.binomania.it/phpBB3/viewtopic.php?t=8371
The advantage of the modification can be seen, compared to the small 4 mm hole.
What is interesting however is that the same thing can be done for the BF1800 with the same methodology, in fact the useful diameter of the BF1800 filter is 19.5 mm, so this BF can be transformed into a BF1900 (perhaps even into a BF1950 ...).
In this case, however, I must point out a ridiculous choice by Lunt in the BF1800 model which does not even lead to exploiting the entire diameter of the BF1800, in fact the IR Cut filter placed at the entrance of the diagonal mirror is approximately 16 mm in diameter, therefore smaller than the 18 mm of the BF and this brings vignetting.
I'm making a tilt adjustment ring to use the BF 1800 filter off its diagonal mirror, so that I can rotate it and use it across its entire diameter (building a new tilting like this viewtopic.php?p=156165#p156165).
Those who do not want to do this, but want to make the most of their B1800 should first eliminate the restriction, widening the entrance hole of the diagonal mirror and inserting a new IR Cut filter at the input by installing a 1.25" IR Cut filter, type UV-IR CUT with KG3 by Smie, or similar.
- bf1800_lunt.jpg (293.76 KiB) Viewed 657 times