MIDWEST OPTICAL BP635-S27.7 Light Bandpass Filter 615-645NM 27.7MM

( Brand: Midwest Optical ), ( Manufacturer Part Number: BP635-S27.7 ), ( Part Type: Light Filter )

Review MIDWEST OPTICAL Light Red Bandpass Filter 615-645nm 27.7mm

The **Midwest Optical BP635-S27.7 Light Bandpass Filter (615 645 nm, 27.7 mm)** is a precision-engineered optical component designed for demanding applications in fluorescence microscopy, spectroscopy, and scientific imaging where narrowband light isolation is critical. This high-quality bandpass filter excels in transmitting a sharply defined spectral range centered at 635 nanometers with a bandwidth of just 30 nm, spanning from 615 nm to 645 nm, while effectively blocking all other wavelengths outside this critical window. The filter s narrow passband ensures minimal spectral overlap with adjacent wavelengths, making it ideal for isolating specific fluorescence emissions or laser lines in experiments where spectral purity is essential. Constructed from high-transmission optical glass and coated with multilayer dielectric thin films, the BP635-S27.7 delivers exceptional optical clarity with a peak transmission efficiency exceeding 90% at the center wavelength, while maintaining a steep rejection slope to suppress stray light and ghosting. Its circular form factor measures precisely 27.7 mm in diameter, compatible with standard filter holders and optical mounts used in microscopes, spectrophotometers, and other imaging systems. The filter s robust construction and durable coating resist environmental degradation, ensuring long-term stability and consistent performance even under prolonged use or exposure to high-intensity light sources. Whether used in fluorescence imaging to isolate red fluorescent dyes like Texas Red or Cy3, in laser-based experiments, or in astronomical observations requiring precise spectral isolation, the BP635-S27.7 provides the reliability and precision required for high-accuracy scientific measurements. Its combination of narrow bandwidth, high transmission, and mechanical durability makes it a versatile and indispensable tool for researchers and engineers working at the forefront of optical science.

**Pros and Cons of buying a Midwest Optical BP635-S27.7 Light Bandpass Filter (615-645 nm, 27.7 mm)**

### **Pros**

1. **High Optical Quality** Midwest Optical is a well-regarded manufacturer known for producing precision optical filters. This bandpass filter is designed to provide narrowband transmission (615 645 nm) with minimal leakage, making it suitable for applications requiring high spectral purity, such as astrophotography, fluorescence imaging, or scientific instrumentation.

2. **Narrow Bandwidth** The 30 nm bandwidth (615 645 nm) allows for selective isolation of specific wavelengths, reducing unwanted light contamination from other spectral regions. This is particularly useful in applications where background noise or stray light could interfere with observations.

3. **Durable Construction** The filter is made from high-quality optical glass with anti-reflective coatings, which enhances transmission efficiency and reduces ghosting or flare. The 27.7 mm size is standard for many astronomical and laboratory setups, ensuring compatibility with existing equipment.

- **Astrophotography**: Isolates the H-alpha emission line (656.3 nm is close to the upper range, but 615 645 nm can still be useful for certain nebulae or calibration).

- **Fluorescence Microscopy**: Can be paired with appropriate excitation sources to isolate emission wavelengths.

- **Spectroscopy**: Helps in isolating specific spectral lines for analysis.

- **Lighting Experiments**: Useful in controlled lighting setups where precise wavelength isolation is needed.

5. **Cost-Effective for the Quality** Compared to some high-end optical manufacturers, Midwest Optical offers competitive pricing without sacrificing performance, making it a practical choice for hobbyists and professionals alike.

6. **Easy to Mount** The 27.7 mm diameter fits standard filter holders, adapters, and telescope drawtube sizes, reducing the need for additional hardware.

7. **Long-Term Stability** Optical filters from reputable manufacturers like Midwest Optical are designed to maintain performance over extended use, provided they are handled carefully (e.g., avoiding scratches or exposure to extreme temperatures).

---

### **Cons**

1. **Limited Bandwidth for Some Applications** The 615 645 nm range does not perfectly align with the most common astrophotography targets (e.g., H-alpha at 656.3 nm or O-III at 496/501 nm). While it can still be useful for certain nebulae or calibration, it may not be ideal for capturing the most popular deep-sky objects like the Orion Nebula or Veil Nebula. Buyers targeting H-alpha specifically may need to consider a BP656 filter instead.

2. **Potential for Light Loss** Bandpass filters inherently reduce the amount of light transmitted compared to unfiltered observations. While this is a trade-off for spectral purity, it may result in longer exposure times in astrophotography, which could be a drawback for faint objects.

3. **Compatibility Issues** While 27.7 mm is a common size, some older or non-standard equipment (e.g., certain cameras or telescopes) may require adapters. Buyers should verify compatibility with their specific setup before purchasing.

4. **No Warranty on Damage from Improper Use** Optical filters can be damaged by scratches, moisture, or improper cleaning. Midwest Optical s warranty likely excludes damage caused by mishandling, so users must handle it with care.

5. **Alternative Manufacturers May Offer Better Performance** Some high-end optical companies (e.g., Chroma, Semrock, or Astrodon) produce bandpass filters with even narrower bandwidths, higher transmission efficiency, or better edge rejection. For critical applications, these may be preferable despite a higher cost.

6. **Shipping and Handling Risks** Optical filters are delicate, and risks such as scratches during shipping exist. While Midwest Optical likely uses protective packaging, buyers should be cautious when receiving the item.

7. **Limited Customization** This is a standard filter, and Midwest Optical may not offer custom sizes, coatings, or bandwidths unless specified separately. Buyers with unique requirements may need to explore other manufacturers.

---

### **Recommendation**

The **Midwest Optical BP635-S27.7 (615 645 nm, 27.7 mm)** is a solid, mid-range optical filter that excels in applications requiring narrowband wavelength isolation where the 615 645 nm range is appropriate. It is particularly well-suited for:

- **Specialized astrophotography** (e.g., capturing specific nebulae or calibration targets within its bandwidth).

- **Fluorescence or scientific imaging** where precise wavelength selection is critical.

- **Budget-conscious buyers** who prioritize quality without the premium cost of high-end alternatives.

**However**, it is not ideal for capturing the most popular astrophotography targets (e.g., H-alpha or O-III nebulae), which require filters centered around 656 nm or 496/501 nm. In such cases, a different bandpass filter would be more appropriate.

- **Buy if:** You need a reliable, cost-effective bandpass filter for applications within the 615 645 nm range (e.g., certain nebulae, fluorescence imaging, or controlled lighting experiments) and your equipment is compatible with the 27.7 mm size.

- **Avoid if:** You are targeting H-alpha or O-III astrophotography, as other filters (e.g., BP656 or BP496/501) would be more effective. Additionally, if you require the absolute highest optical performance (e.g., for professional spectroscopy), consider premium alternatives.

- **Consider alternatives:** For astrophotography, explore filters like the **Optolong L-Pro** (broadband) or **Astrodon H-alpha** (656 nm) if your primary goal is capturing common deep-sky objects. For laboratory or scientific use, verify the exact wavelength requirements before purchasing.

Overall, this filter is a practical choice for its intended applications, offering a good balance of performance and affordability. Always handle it carefully to preserve its optical quality.

Details:

Filter Range: 615-645nm. Overall OD: 42.5mm. Specifications: model #: BP635-S27.7. Slip Mount: 27.7mm.

This is a surplus item. Midwest Optical.

part #: bp635s277 price

• $79.00

specifications industrlasemr:

• brand: Midwest Optical
• mpn: Bp635-s27.7
• part type: Light Filter

general industrlasemr:

• Medical/Lab Equipment Attachments Accessories > Lamps, Bulbs Laser Components > Other Medical/Lab Equipment Lamps Bulbs
• condition: Used

seller industrlasemr:

• city: Osseo, Minnesota
• # reviews: 45422
• rating: 100.0%

shipping industrlasemr:

• service: USPS First Class, USPS Priority Mail Padded Flat Rate Envelope, UPS Next Day Air
• class: Standard, Expedited, One-day
• transit: 2-4 Days
• cost: $0.00
• type: Calculated
• carrier: USPS, UPS

payments industrlasemr:

• cash
• wallet: Paypal
• credit card: Diners-club
• other

offer industrlasemr:

• options: Ship-to-home
• quantity: 1
• availability: In Stock
• best offers: True
• started: April 28, 2026
• sold: 0

returns industrlasemr:

• policy: Returns Accepted
• method: Money back
• paid by: Seller
• time: 30 Days

Midwest Optical BP635-S27.7 Is Similar To:

• Midwest Optical Sp700-58 Midopt Near Ir Dichroic Block (43.5% similar) Comes in original case. See photos for details...(February 5th, 2026)
• Midwest Optical Bp470-s27.7 Blue Light Bandpass Filter 425-495nm 27.7mm (85.1% similar) Overall OD: 42.5MM. This is a surplus item. Midwest Optical. Slip mount: 27.7MM. Specifications: model #: BP470-S27.7. Filter range: 425-495NM...(May 1st, 2026)